U.S. patent application number 16/213600 was filed with the patent office on 2019-04-11 for polymeric membranes, compositions, and methods of making the same.
This patent application is currently assigned to Cooper-Standard Automotive Inc.. The applicant listed for this patent is Cooper-Standard Automotive Inc.. Invention is credited to Krishnamachari Gopalan, Roland Herd-Smith, Gending Ji, Robert J. Lenhart.
Application Number | 20190105883 16/213600 |
Document ID | / |
Family ID | 65993828 |
Filed Date | 2019-04-11 |
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United States Patent
Application |
20190105883 |
Kind Code |
A1 |
Gopalan; Krishnamachari ; et
al. |
April 11, 2019 |
POLYMERIC MEMBRANES, COMPOSITIONS, AND METHODS OF MAKING THE
SAME
Abstract
A membrane that includes: at least one layer comprising a first
silane-crosslinked polyolefin elastomer having a density from about
0.80 g/cm.sup.3to about 1.75 g/cm.sup.3. The silane-crosslinked
polyolefin elastomer can exhibit a crystallinity of from about 5%
to about 25% and a glass transition temperature of from about
-75.degree. C. to about -25.degree. C. Further, the first
silane-crosslinked polyolefin elastomer can comprise a first
polyolefin having a density less than 0.90 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst. In addition, the at least one layer can
comprise a thickness from about 0.2 mm to about 3 mm.
Inventors: |
Gopalan; Krishnamachari;
(Troy, MI) ; Lenhart; Robert J.; (Fort Wayne,
IN) ; Ji; Gending; (Waterloo, Ontario, CA) ;
Herd-Smith; Roland; (Brignancourt, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cooper-Standard Automotive Inc. |
Novi |
MI |
US |
|
|
Assignee: |
Cooper-Standard Automotive
Inc.
Novi
MI
|
Family ID: |
65993828 |
Appl. No.: |
16/213600 |
Filed: |
December 7, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15836417 |
Dec 8, 2017 |
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16213600 |
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62497959 |
Dec 10, 2016 |
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62497954 |
Dec 10, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E04D 5/10 20130101; B32B
2305/72 20130101; C08L 23/0815 20130101; B32B 27/18 20130101; C08L
2312/08 20130101; B32B 5/024 20130101; E04D 5/06 20130101; B32B
2307/704 20130101; C08L 23/12 20130101; C08L 2201/02 20130101; B32B
2307/712 20130101; C08L 23/14 20130101; B32B 27/32 20130101; C08L
23/0815 20130101; C08K 3/22 20130101; C08K 2003/2227 20130101; C08K
2003/2224 20130101; B32B 2307/72 20130101; B32B 2307/3065 20130101;
B32B 2419/06 20130101; E04D 12/002 20130101; C08K 3/011
20180101 |
International
Class: |
B32B 27/32 20060101
B32B027/32; B32B 27/18 20060101 B32B027/18; B32B 5/02 20060101
B32B005/02; C08L 23/08 20060101 C08L023/08; C08L 23/14 20060101
C08L023/14; C08K 3/22 20060101 C08K003/22; E04D 12/00 20060101
E04D012/00 |
Claims
1. A membrane, comprising: at least one layer comprising a first
silane-crosslinked polyolefin elastomer having a density from about
0.80 g/cm.sup.3 to about 1.75 g/cm.sup.3.
2. The membrane according to claim 1, wherein the first
silane-crosslinked polyolefin elastomer exhibits a crystallinity of
from about 5% to about 25% and a glass transition temperature of
from about -75.degree. C. to about -25.degree. C.
3. The membrane according to claim 1, wherein the first
silane-crosslinked polyolefin elastomer comprises a first
polyolefin having a density less than 0.90 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
4. The membrane according to claim 1, wherein the first
silane-crosslinked polyolefin elastomer is selected from the group
consisting of a propylene/.alpha.-olefin copolymer and a blend of
propylene/.alpha.-olefin copolymer with an ethylene/.alpha.-olefin
copolymer.
5. The membrane according to claim 1, wherein the at least one
layer comprises a thickness from about 0.2 mm to about 3 mm.
6. The membrane according to claim 1, wherein the at least one
layer comprises a first silane-crosslinked polyolefin elastomer
having a density from about 0.80 g/cm.sup.3to about 1.45
g/cm.sup.3, and further wherein the first silane-crosslinked
polyolefin elastomer comprises a first polyolefin having a density
less than 0.90 g/cm.sup.3, a second polyolefin, a silane
crosslinker, a grafting initiator, and a condensation catalyst.
7. The membrane according to claim 6, further comprising: a scrim
layer that is contiguous with the at least one layer.
8. The membrane according to claim 6, wherein the membrane is
configured as a roofing membrane.
9. The membrane of claim 6, wherein the at least one layer is
characterized by a weathering color difference from about 0.4
.DELTA.E to about 3 .DELTA.E after 2000 cycles of testing, as
measured according to ASTM G155, and further wherein the at least
one layer is characterized by a heat aging resistance after
exposure to 115.degree. C. for 168 hours given by a tensile
strength from about 5 MPa to about 15 MPa, an elongation from about
100% to about 300%, and a 100% elastic modulus from about 3 MPa to
about 12 MPa.
10. The membrane of claim 6, wherein the at least one layer is
further characterized by a heat aging resistance after exposure to
115.degree. C. for 168 hours given by a tensile strength from about
9.5 MPa to about 11.5 MPa, an elongation from about 100% to about
1000%, and a 100% elastic modulus from about 6.6 MPa to about 9.0
MPa.
11. The membrane of claim 6, wherein the at least one layer further
comprises a flame retardant, the flame retardant comprising
magnesium di hydroxide or aluminum tri hydroxide from about 20 wt.
% to about 70 wt. %.
12. A membrane, comprising: a first layer comprising a first
silane-crosslinked polyolefin elastomer having a density from about
0.80 g/cm.sup.3to about 1.75 g/cm.sup.3; and a second layer
comprising a second silane-crosslinked polyolefin elastomer having
a density from about 0.80 g/cm.sup.3 to about 1.75 g/cm.sup.3.
13. The membrane according to claim 12, wherein one or both of the
first and second silane-crosslinked polyolefin elastomers exhibits
a crystallinity of from about 5% to about 25% and a glass
transition temperature of from about -75.degree. C. to about
-25.degree. C.
14. The membrane according to claim 12, wherein one or both of the
first and second silane-crosslinked polyolefin elastomers comprises
a first polyolefin having a density less than 0.90 g/cm.sup.3, a
second polyolefin, a silane crosslinker, a grafting initiator, and
a condensation catalyst.
15. The membrane according to claim 12, wherein one or both of the
first and second silane-crosslinked polyolefin elastomers is
selected from the group consisting of a propylene/.alpha.-olefin
copolymer and a blend of propylene/.alpha.-olefin copolymer with an
ethylene/.alpha.-olefin copolymer.
16. A method of making a membrane, comprising: processing a
composition comprising a first polyolefin having a density less
than 0.90 g/cm.sup.3, a second polyolefin, a silane crosslinker, a
grafting initiator, and a condensation catalyst to form at least
one layer; and crosslinking the at least one layer at a curing
temperature and a curing humidity, wherein the crosslinking is
conducted until the at least one layer comprises a density from
about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3.
17. The method according to claim 16, wherein the curing
temperature is an ambient temperature.
18. The method according to claim 16, wherein the curing humidity
is an ambient humidity.
19. The method according to claim 16, wherein the processing
comprises one or more process steps selected from the group
consisting of extruding, blow molding, casting and calendaring.
20. The method according to claim 16, further comprising:
processing a scrim layer with the at least one layer such that the
scrim layer is contiguous to the at least one layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This continuation-in-part application claims priority under
35 U.S.C. .sctn. 120 to U.S. patent application Ser. No.
15/836,417, filed Dec. 8, 2017, entitled "ROOFING MEMBRANES,
COMPOSITIONS, AND METHODS OF MAKING THE SAME," which is a
non-provisional application that claims priority under 35 U.S.C.
.sctn. 119(e) to U.S. Provisional Patent Application No.
62/497,959, filed Dec. 10, 2016, entitled "HOSE, COMPOSITION
INCLUDING SILANE-GRAFTED POLYOLEFIN, AND PROCESS OF MAKING A HOSE,"
and to U.S. Provisional Patent Application No. 62/497,954 filed
Dec. 10, 2016, entitled "WEATHERSTRIP, COMPOSITION INCLUDING
SILANE-GRAFTED POLYOLEFIN, AND PROCESS OF MAKING A WEATHERSTRIP,"
all of which are herein incorporated by reference in their
entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure generally relates to compositions
that may be used to form membranes for roofing and non-roofing
applications, and more particularly, to silane-grafted polyolefin
elastomer compositions used to form membranes and roofing
membranes, and methods for manufacturing these compositions,
membranes and roofing membranes.
BACKGROUND OF THE DISCLOSURE
[0003] Polymeric membranes may be a single layer or may be composed
of multiple layers. Each of the respective layers in the membrane,
whether one layer or multiple layers, should exhibit a variety of
different material properties, depending on the end use application
(e.g., roofing membrane, conveyor belt, mattress cover, wire
insulation, liner for containment vessel, etc.). For membranes
configured as roofing membranes, the membrane may be a single layer
or may be composed of multiple layers and may contain a reinforcing
fabric or scrim reinforcement material as on or more additional
layers. The layer(s) should exhibit particular properties given
their exposure to the sun and the elements. These properties can
include: good adhesion, UV resistance, weatherability (durability),
flame retardance, flexibility, chemical resistance and longevity.
In addition, roofing membranes should preferably be capable of
forming hot-air welded seams.
[0004] Many different polymer systems are available to be used for
membranes. For membranes configured as roofing membranes, the most
commonly used polymer systems include thermoplastic polyolefin
(TPO), ethylene propylene diene monomer (EPDM), and polyvinyl
chloride (PVC). Depending on the material(s) selected, different
advantages and disadvantages are typically observed. TPO membranes
are widely available, affordable, and typically white, but are
susceptible to low flexibility at low temperatures. EPDM membranes
are made from the readily available EPDM synthetic rubber, but
roughly 95% of all EPDM roofing membranes produced are black while
federal and state building regulators are starting to push for
white roofing membranes. Lastly, PVC membranes are widely available
and offer excellent puncture, heat-weldability, colorability, and
heat resistant qualities, but these membranes can be expensive to
manufacture and suffer from variability in properties as produced
by different manufacturers.
[0005] Mindful of the advantages and drawbacks for the various TPO,
EPDM, and PVC materials used to make membranes, including roofing
membranes, manufacturers have a need for the development of new
polymer compositions and methods of making membranes that are
amenable to simpler processing techniques with less production
variability, lighter in weight and color, and have superior
durability over a longer period of time.
SUMMARY OF THE DISCLOSURE
[0006] According to a first aspect of the present disclosure, a
membrane is provided that includes: at least one layer comprising a
first silane-crosslinked polyolefin elastomer having a density from
about 0.80 g/cm.sup.3 to about 1.75 g/cm.sup.3. Embodiments of the
first aspect can be configured such that the silane-crosslinked
polyolefin elastomer exhibits a crystallinity of from about 5% to
about 25% and a glass transition temperature of from about
-75.degree. C. to about -25.degree. C. Further, the first
silane-crosslinked polyolefin elastomer can comprise a first
polyolefin having a density less than 0.90 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst. In addition, the at least one layer can
comprise a thickness from about 0.2 mm to about 3 mm.
[0007] According to a second aspect of the present disclosure, a
membrane is provided that includes: a first layer comprising a
first silane-crosslinked polyolefin elastomer having a density from
about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3; and a second layer
comprising a second silane-crosslinked polyolefin elastomer having
a density from about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3.
According to a third aspect of the present disclosure, a method of
making a membrane is provided. The method includes: processing a
composition comprising a first polyolefin having a density less
than 0.90 g/cm.sup.3, a second polyolefin, a silane crosslinker, a
grafting initiator, and a condensation catalyst to form at least
one layer; and crosslinking the at least one layer at a curing
temperature and a curing humidity, wherein the crosslinking is
conducted until the at least one layer comprises a density from
about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3.
[0008] These and other aspects, objects, and features of the
present disclosure will be understood and appreciated by those
skilled in the art upon studying the following specification,
claims, and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] In the drawings:
[0010] FIG. 1 is a cross-sectional view of a membrane according to
some aspects of the present disclosure;
[0011] FIG. 2 is a schematic reaction pathway used to produce a
silane-crosslinked polyolefin elastomer according to some aspects
of the present disclosure;
[0012] FIG. 3 is a flow diagram of a method for making a single ply
membrane with a silane-crosslinked polyolefin elastomer using a
two-step Sioplas approach according to some aspects of the present
disclosure;
[0013] FIG. 4A is a schematic cross-sectional view of a reactive
twin-screw extruder according to some aspects of the present
disclosure;
[0014] FIG. 4B is a schematic cross-sectional view of a
single-screw extruder according to some aspects of the present
disclosure;
[0015] FIG. 5 is a flow diagram of a method for making a single ply
membrane with a silane-crosslinked polyolefin elastomer using a
one-step Monosil approach according to some aspects of the present
disclosure;
[0016] FIG. 6 is a schematic cross-sectional view of a reactive
single-screw extruder according to some aspects of the present
disclosure;
[0017] FIG. 7 is a graph illustrating the stress/strain behavior of
a silane-crosslinked polyolefin elastomer, according to aspects of
the disclosure, as compared to conventional EPDM compounds;
[0018] FIGS. 8A and 8B are stress vs. elongation plots of a
membrane comprising a silane-crosslinked polyolefin elastomer
suitable for roofing membrane, according to aspects of the
disclosure;
[0019] FIG. 9 is a relaxation plot of an exemplary
silane-crosslinked polyolefin elastomer, suitable for a membrane
according to aspects of the disclosure, and comparative EPDM
cross-linked materials; and
[0020] FIG. 10 is a compression set plot of an exemplary
silane-crosslinked polyolefin elastomer suitable for a membrane
according to aspects of the disclosure, and a comparative EPDM
cross-linked material.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0021] For purposes of description herein the terms "upper,"
"lower," "right," "left," "rear," "front," "vertical,"
"horizontal," and derivatives thereof shall relate to the roofing
membranes of the disclosure as shown in FIG. 1. However, it is to
be understood that the device may assume various alternative
orientations and step sequences, except where expressly specified
to the contrary. It is also to be understood that the specific
devices and processes illustrated in the attached drawings, and
described in the following specification are simply exemplary
embodiments of the inventive concepts defined in the appended
claims. Hence, specific dimensions and other physical
characteristics relating to the embodiments disclosed herein are
not to be considered as limiting, unless the claims expressly state
otherwise.
[0022] All ranges disclosed herein are inclusive of the recited
endpoint and independently combinable (for example, the range of
"from 2 to 10" is inclusive of the endpoints, 2 and 10, and all the
intermediate values). The endpoints of the ranges and any values
disclosed herein are not limited to the precise range or value;
they are sufficiently imprecise to include values approximating
these ranges and/or values.
[0023] A value modified by a term or terms, such as "about" and
"substantially," may not be limited to the precise value specified.
The approximating language may correspond to the precision of an
instrument for measuring the value. The modifier "about" should
also be considered as disclosing the range defined by the absolute
values of the two endpoints. For example, the expression "from
about 2 to about 4" also discloses the range "from 2 to 4."
[0024] As used herein, the term "and/or," when used in a list of
two or more items, means that any one of the listed items can be
employed by itself, or any combination of two or more of the listed
items can be employed. For example, if a composition is described
as containing components A, B, and/or C, the composition can
contain A alone; B alone; C alone; A and B in combination; A and C
in combination; B and C in combination; or A, B, and C in
combination.
[0025] For purposes of this disclosure, the term "coupled" (in all
of its forms, couple, coupling, coupled, etc.) generally means the
joining of two components directly or indirectly to one another.
Such joining may be stationary in nature or movable in nature. Such
joining may be achieved with the two components and any additional
intermediate members being integrally formed as a single unitary
body with one another or with the two components. Such joining may
be permanent in nature or may be removable or releasable in nature
unless otherwise stated.
[0026] Referring to FIG. 1, a membrane 10 is disclosed. The
membrane 10, as shown in FIG. 1, includes a top layer 14 having an
optional flame retardant and a first silane-crosslinked polyolefin
elastomer having a density from about 0.80 g/cm.sup.3 to about 1.75
g/cm.sup.3; an optional scrim layer 26; and a bottom layer 38
having an optional flame retardant and a second silane-crosslinked
polyolefin elastomer with a density from about 0.80 g/cm.sup.3 to
about 1.75 g/cm.sup.3. It should be understood that the membrane 10
can also comprise one or more layers 14, with an optional scrim
layer 26 and optional bottom layer 38. Similarly, the membrane 10
can also comprise one or more bottom layers 38 with an optional
scrim layer 26 and optional top layer 14. Further, according to
some embodiments of the membrane 10, the membrane 10 is configured
as roofing membrane. Further, according to some embodiments of the
membrane 10, one or both of the top and bottom layers 14, 38 of the
membrane can exhibit a compression set of from about 5.0% to about
35.0%, as measured according to ASTM D 395 (22 hrs. @ 70.degree.
C.).
[0027] More generally, the membrane 10 depicted in FIG. 1 can be
employed in a variety of end use applications, including
roofing-related applications. These other applications and end uses
include, but are not limited to, conveyor belts, mattress covers,
and wire insulation. The particular material properties, low
processing costs and other advantages associated with the membranes
10 of the disclosure that make them well-suited for roofing
applications are also relevant to these other non-roofing
applications. For example, heat, flame and weathering resistance of
the membranes 10, e.g., as configured for roofing membranes, also
makes them well-suited for wire insulation applications. As another
example, the chemical resistance of the membranes 10, e.g., as
configured for roofing membranes, also makes them well-suited for
conveyor belt applications in which the conveyor belt is
transporting chemicals and other materials that might otherwise
degrade a conventional conveyor belt lacking such chemical
resistance. As a further example, the water impermeability of the
membranes 10 also makes them well-suited as liners for pools,
man-made ponds, and other containment vessels.
[0028] According to embodiments, a membrane 10, as configured for a
roofing membrane, can exhibit at least the following mechanical
properties as outlined by the ASTM specification for TPO roofing
membranes: 1) a tensile strength (CD and MD) greater than 10 MPa;
2) an elongation at break (CD and MD) greater than 500%; 3) an
elastic modulus (CD and MD) of less than 100 MPa; and 4) a flame
retardance rating of classification D as measured in accordance
with the EN ISO 11925-2 surface exposure test.
[0029] Referring again to FIG. 1, a cross-sectional view of a
membrane 10 is provided, which can be configured as a single-ply
membrane or single-ply roofing membrane according to some
embodiments. The membrane 10 includes the top layer 14 with a first
and a second surface 18, 22. If present, the scrim layer 26 (also
referred to as scrim 26) has a third and a fourth surface 30, 34
where the third surface 30 of the scrim 26 is coupled to the second
surface 22 of the top layer 14. The membrane 10 additionally
includes a bottom layer 38 with a fifth and a sixth surface 42, 46,
where the fifth surface 42 of the bottom layer 38 is coupled to the
fourth surface 34 of the scrim 26. Unless otherwise denoted in the
disclosure, a membrane 10 and a single ply membrane 10
interchangeably mean a single ply made from the top layer 14, scrim
layer 26, and bottom layer 38. In some aspects, however, the
membrane 10 may include a single ply membrane, a double ply
membrane, or more than two plies. In embodiments of the membrane 10
containing a plurality of plies, each ply can comprise a top layer
14, scrim layer 26 and bottom layer 38. In other embodiments of the
membrane 10 containing a plurality of plies, each ply can comprise
one or more of the top layer 14, scrim layer 26 and bottom layer
38.
[0030] The optional scrim layer 26 disposed between the top and
bottom layers 14, 38 shown in FIG. 1 (e.g., in an arrangement that
is contiguous with layers 14, 38) can serve as a reinforcement in
the membrane 10, thus adding to its structural integrity. Materials
that can be used for the scrim layers 26 may include, for example,
woven and/or non-woven fabrics, fiberglass, and/or polyester. In
some aspects, additional materials that can be used for the scrim
layers 26 can include synthetic materials such as polyaramids
(e.g., KEVLAR.TM. and TWARON.TM.), polyamides, polyesters (e.g.,
RAYON.TM., NOMEX.TM., and TECHNORA.TM.), or a combination thereof.
In some aspects, the scrim layer 26 may include aramids,
polyamides, and/or polyesters. In some aspects, a tenacity of the
scrim layer 26 may range from about 100 to about 3000 denier. In
other aspects, the scrim layer 26 may have a tenacity ranging from
about 500 to about 1500 denier. In still other aspects, scrim layer
26 may have a tenacity of about 1000 denier. In some aspects, scrim
layer 26 may have a tensile strength of greater than about 14 kN
per meter (80 pounds force per inch). In other aspects, the scrim
layer 26 may have a tensile strength of greater than about 10 kN
per meter, greater than about 15 kN per meter, greater than about
20 kN per meter, or greater than about 25 kN per meter. Depending
on the desired properties of the membrane 10, the scrim layer 26
may be varied as needed to suit particular membrane or roofing
membrane applications, designs and configurations. One of ordinary
skill in the art would appreciate that such characteristics can be
varied without departing from the present disclosure.
[0031] The single ply membranes 10 disclosed herein, e.g., as
roofing membranes, can have a variety of different dimensions. In
some aspects, membranes 10 may have a length from about 30 feet to
about 200 feet and a width from about 4 feet to about 12 feet. In
some aspects, the membranes 10 may have a width of about 10 feet.
Variations in the width may provide for various advantages. For
example, in some aspects, membranes 10 having smaller widths may
advantageously allow for greater ease in assembly of a roofing
structure. Smaller widths may also advantageously allow for greater
ease in rolling or packaging of a manufactured membrane. Larger
widths may advantageously allow for greater structure integrity,
fast installation and/or improve the stability of a roofing
structure comprising these membranes.
[0032] Referring again to the membrane 10 depicted in FIG. 1, the
thickness of the membrane can range from about 0.2 mm to about 5
mm, from about 0.2 mm to about 4 mm, from about 0.2 mm to about 3
mm, from about 0.2 mm to about 2 mm, from about 0.2 mm to about 1
mm, from about 0.5 mm to about 5 mm, from about 0.5 mm to about 4
mm, from about 0.5 mm to about 3 mm, from about 0.5 mm to about 2
mm, from about 0.5 mm to about 1 mm, from about 1 mm to about 5 mm,
from about 1 mm to about 4 mm, from about 1 mm to about 3 mm, from
about 1 mm to about 2 mm, and all thickness values between these
ranges. It should also be understood that the foregoing thickness
values of the membrane 10 are applicable to the membrane 10 in any
of its viable configurations according to the principles of this
disclosure, whether including one or more top layer 14, one or more
bottom layer 38 and the optional scrim layer(s) 26. According to
some implementations of the membrane 10 configured in the form of a
roofing membrane, the thickness of the membrane can range from
about 0.254 mm (10 mils) to about 2.54 mm (100 mils), from about
1.02 mm (40 mils) to about 1.52 mm (60 mils), and all thickness
values between these ranges.
[0033] Numerous different flame retardants may be used in
combination with the first and second silane-crosslinkable
polyolefin elastomer employed in the top and bottom layers 14, 38
of the membrane 10, particularly as configured for roofing
membranes. For example, magnesium di hydroxide (e.g., MAGNIFIN.RTM.
H5A from Huber Engineered Materials) and/or aluminum tri hydroxide
may provide flame retardant properties in the layers 14, 38.
Magnesium di hydroxide and/or aluminum tri hydroxide may be
extruded or blended with the silane-grafted polyolefin elastomer to
ensure complete dispersal in the composition blend. In some
aspects, the magnesium di hydroxide and/or aluminum tri hydroxide
is blended with the silane-grafted polyolefin elastomer in an
amount up to 70 wt. % magnesium di hydroxide and/or aluminum tri
hydroxide. In another exemplary embodiment, the magnesium di
hydroxide and/or the aluminum tri hydroxide in the silane-grafted
polyolefin elastomer can make up between about 20 wt. % and 75 wt.
% of the membrane composition. Further, some implementations of the
membrane 10 in the disclosure, including implementations in which
the membrane 10 is configured for a roofing membrane, do not employ
any materials understood by those of ordinary skill in the field of
the disclosure as fire retardant materials.
[0034] The disclosure focuses on the compositions, methods of
making the composition, and methods of making membranes, along with
roofing membranes, and other applications, with these compositions.
The polymeric membranes, e.g., membranes 10, can be employed in
roofing membranes and other applications that can make use of
membranes (e.g., conveyor belts, wire insulation, mattress covers,
liners for water containment vessels, etc.). The disclosure also
focuses on the corresponding material properties for the
silane-crosslinked polyolefin elastomer used to make these
membranes 10 (e.g., as configured for roofing membranes), e.g., the
top and bottom layers 14, 38 of single ply roofing membranes 10 (as
depicted in FIG. 1), single layers, membranes, membrane elements
and laminates consistent with one or more of the top and bottom
layers 14, 38 of the membrane 10, along with layers of other
membranes 10 consistent with the principles of this disclosure. The
layers 14, 38 of the membrane 10 are formed from a silane-grafted
polyolefin where the silane-grafted polyolefin may have a catalyst
added to form a silane-crosslinkable polyolefin elastomer. This
silane-crosslinkable polyolefin may then be crosslinked upon
exposure to moisture and/or heat to form the final
silane-crosslinked polyolefin elastomer or blend. In aspects, the
silane-crosslinked polyolefin elastomer or blend includes a first
polyolefin having a density less than 0.90 g/cm.sup.3, a second
polyolefin (e.g., as having a crystallinity of less than 40%), a
silane crosslinker, a grafting initiator, and a condensation
catalyst.
First Polyolefin
[0035] The first polyolefin can be a polyolefin elastomer including
an olefin block copolymer, an ethylene/.alpha.-olefin copolymer, a
propylene/.alpha.-olefin copolymer, EPDM, EPM, or a mixture of two
or more of any of these materials. Exemplary block copolymers
include those sold under the trade names INFUSE.TM., an olefin
block co-polymer (the Dow Chemical Company) and SEPTON.TM.
V-SERIES, a styrene-ethylene-butylene-styrene block copolymer
(Kuraray Co., LTD.). Exemplary ethylene/.alpha.-olefin copolymers
include those sold under the trade names TAFMER.TM. (Mitsui
Chemicals, Inc.), ENGAGE.TM. (Dow Chemical Company). Exemplary
propylene/.alpha.-olefin copolymers include those sold under the
trade name VISTAMAXX.TM. (Exxon Mobil Chemical Company), TAFMER.TM.
XM (Mitsui Chemical Company), and VERSIFY.TM. (Dow Chemical
Company). The EPDM may have a diene content of from about 0.5 to
about 10 wt. %. The EPM may have an ethylene content of 45 wt. % to
75 wt. %.
[0036] The term "comonomer" refers to olefin comonomers which are
suitable for being polymerized with olefin monomers, such as
ethylene or propylene monomers. Comonomers may comprise but are not
limited to aliphatic C.sub.2-C.sub.20 .alpha.-olefins. Examples of
suitable aliphatic C.sub.2-C.sub.20 .alpha.-olefins include
ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene,
1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene,
1-octadecene and 1-eicosene. In an embodiment, the comonomer is
vinyl acetate. The term "copolymer" refers to a polymer, which is
made by linking more than one type of monomer in the same polymer
chain. The term "homopolymer" refers to a polymer which is made by
linking olefin monomers, in the absence of comonomers. The amount
of comonomer can, in some embodiments, be from greater than 0 wt. %
to about 12 wt. % based on the weight of the polyolefin, including
from greater than 0 wt. % to about 9 wt. %, and from greater than 0
wt. % to about 7 wt. %. In some embodiments, the comonomer content
is greater than about 2 mol % of the final polymer, including
greater than about 3 mol % and greater than about 6 mol %. The
comonomer content may be less than or equal to about 30 mol %. A
copolymer can be a random or block (heterophasic) copolymer. In
some embodiments, the polyolefin is a random copolymer of propylene
and ethylene.
[0037] In some aspects, the first polyolefin is selected from the
group consisting of: an olefin homopolymer, a blend of
homopolymers, a copolymer made using two or more olefins, a blend
of copolymers each made using two or more olefins, and a
combination of olefin homopolymers blended with copolymers made
using two or more olefins. The olefin may be selected from
ethylene, propylene, 1-butene, 1-propene, 1-hexene, 1-octene, and
other higher 1-olefin. The first polyolefin may be synthesized
using many different processes (e.g., using gas phase and solution
based metallocene catalysis and Ziegler-Natta catalysis) and
optionally using a catalyst suitable for polymerizing ethylene
and/or .alpha.-olefins. In some aspects, a metallocene catalyst may
be used to produce low density ethylene/.alpha.-olefin
polymers.
[0038] In some aspects, the polyethylene used for the first
polyolefin can be classified into several types including, but not
limited to, LDPE (Low Density Polyethylene), LLDPE (Linear Low
Density Polyethylene), and HDPE (High Density Polyethylene). In
other aspects, the polyethylene can be classified as Ultra High
Molecular Weight (UHMW), High Molecular Weight (HMW), Medium
Molecular Weight (MMW) and Low Molecular Weight (LMW). In still
other aspects, the polyethylene may be an ultra-low density
ethylene elastomer.
[0039] In some aspects, the first polyolefin may include a
LDPE/silane copolymer or blend. In other aspects, the first
polyolefin may be polyethylene that can be produced using any
catalyst known in the art including, but not limited to, chromium
catalysts, Ziegler-Natta catalysts, metallocene catalysts or
post-metallocene catalysts.
[0040] In some aspects, the first polyolefin may have a molecular
weight distribution M.sub.w/M.sub.n of less than or equal to about
5, less than or equal to about 4, from about 1 to about 3.5, or
from about 1 to about 3.
[0041] The first polyolefin may be present in an amount of from
greater than 0 to about 100 wt. % of the composition. In some
embodiments, the amount of polyolefin elastomer is from about 30
wt. % to about 70 wt. %. In some aspects, the first polyolefin fed
to an extruder can include from about 50 wt. % to about 80 wt. % of
an ethylene/.alpha.-olefin copolymer, including from about 60 wt. %
to about 75 wt. %, and from about 62 wt. % to about 72 wt. %.
[0042] The first polyolefin may have a melt index (T2), measured at
190.degree. C. under a 2.16 kg load, of from about 2 g/10 min to
about 3,500 g/10 min or from about 20.0 g/10 min to about 3,500
g/10 min, including from about 250 g/10 min to about 1,900 g/10 min
and from about 300 g/10 min to about 1,500 g/10 min. In some
aspects, the first polyolefin has a fractional melt index of from
0.5 g/10 min to about 3,500 g/10 min.
[0043] In some aspects, the density of the first polyolefin is less
than 0.90 g/cm.sup.3, less than about 0.89 g/cm.sup.3, less than
about 0.88 g/cm.sup.3, less than about 0.87 g/cm.sup.3, less than
about 0.86 g/cm.sup.3, less than about 0.85 g/cm.sup.3, less than
about 0.84 g/cm.sup.3, less than about 0.83 g/cm.sup.3, less than
about 0.82 g/cm.sup.3, less than about 0.81 g/cm.sup.3, or less
than about 0.80 g/cm.sup.3. In other aspects, the density of the
first polyolefin may be from about 0.85 g/cm.sup.3to about 0.89
g/cm.sup.3, from about 0.85 g/cm.sup.3to about 0.88 g/cm.sup.3,
from about 0.84 g/cm.sup.3to about 0.88 g/cm.sup.3, or from about
0.83 g/cm.sup.3to about 0.87 g/cm.sup.3. In still other aspects,
the density is at about 0.84 g/cm.sup.3, about 0.85 g/cm.sup.3,
about 0.86 g/cm.sup.3, about 0.87 g/cm.sup.3, about 0.88
g/cm.sup.3, or about 0.89 g/cm.sup.3.
[0044] The percent crystallinity of the first polyolefin may be
less than about 60%, less than about 50%, less than about 40%, less
than about 35%, less than about 30%, less than about 25%, or less
than about 20%. The percent crystallinity may be at least about
10%. In some aspects, the crystallinity is in the range of from
about 2% to about 60%.
Second Polyolefin
[0045] The second polyolefin can be a polyolefin elastomer
including an olefin block copolymer, an ethylene/.alpha.-olefin
copolymer, a propylene/.alpha.-olefin copolymer, EPDM, EPM, or a
mixture of two or more of any of these materials. Exemplary block
copolymers include those sold under the trade names INFUSE.TM. (the
Dow Chemical Company) and SEPTON.TM. V-SERIES (Kuraray Co., LTD.).
Exemplary ethylene/.alpha.-olefin copolymers include those sold
under the trade names TAFMER.TM. (Mitsui Chemicals, Inc.) and
ENGAGE.TM. (Dow Chemical Company). Exemplary
propylene/.alpha.-olefin copolymers include those sold under the
trade name TAFMER.TM. XM grades (Mitsui Chemical Company) and
VISTAMAXX.TM. (Exxon Mobil Chemical Company). The EPDM may have a
diene content of from about 0.5 to about 10 wt. %. The EPM may have
an ethylene content of 45 wt. % to 75 wt. %.
[0046] In some aspects, the second polyolefin is selected from the
group consisting of: an olefin homopolymer, a blend of
homopolymers, a copolymer made using two or more olefins, a blend
of copolymers each made using two or more olefins, and a blend of
olefin homopolymers with copolymers made using two or more olefins.
The olefin may be selected from ethylene, propylene, 1-butene,
1-propene, 1-hexene, 1-octene, and other higher 1-olefin. The first
polyolefin may be synthesized using many different processes (e.g.,
using gas phase and solution based metallocene catalysis and
Ziegler-Natta catalysis) and optionally using a catalyst suitable
for polymerizing ethylene and/or .alpha.-olefins. In some aspects,
a metallocene catalyst may be used to produce low density
ethylene/.alpha.-olefin polymers.
[0047] In some aspects, the second polyolefin may include a
polypropylene homopolymer, a polypropylene copolymer, a
polyethylene-co-propylene copolymer, or a mixture thereof. Suitable
polypropylenes include but are not limited to polypropylene
obtained by homopolymerization of propylene or copolymerization of
propylene and an .alpha.-olefin comonomer. In some aspects, the
second polyolefin may have a higher molecular weight and/or a
higher density than the first polyolefin.
[0048] In some embodiments, the second polyolefin may have a
molecular weight distribution M.sub.w/M.sub.n of less than or equal
to about 5, less than or equal to about 4, from about 1 to about
3.5, or from about 1 to about 3.
[0049] The second polyolefin may be present in an amount of from
greater than 0 wt. % to about 100 wt. % of the composition. In some
embodiments, the amount of polyolefin elastomer is from about 30
wt. % to about 70 wt. %. In some embodiments, the second polyolefin
fed to the extruder can include from about 10 wt. % to about 50 wt.
% polypropylene, from about 20 wt. % to about 40 wt. %
polypropylene, or from about 25 wt. % to about 35 wt. %
polypropylene. The polypropylene may be a homopolymer or a
copolymer.
[0050] The second polyolefin may have a melt index (T2), measured
at 190.degree. C. under a 2.16 kg load, of from about 2 g/10 min to
about 3,500 g/10 min or from about 20.0 g/10 min to about 3,500
g/10 min, including from about 250 g/10 min to about 1,900 g/10 min
and from about 300 g/10 min to about 1,500 g/10 min. In some
embodiments, the second polyolefin has a fractional melt index of
from 0.5 g/10 min to about 3,500 g/10 min.
[0051] In some aspects, the density of the second polyolefin is
less than 0.90 g/cm.sup.3, less than about 0.89 g/cm.sup.3, less
than about 0.88 g/cm.sup.3, less than about 0.87 g/cm.sup.3, less
than about 0.86 g/cm.sup.3, less than about 0.85 g/cm.sup.3, less
than about 0.84 g/cm.sup.3, less than about 0.83 g/cm.sup.3, less
than about 0.82 g/cm.sup.3, less than about 0.81 g/cm.sup.3, or
less than about 0.80 g/cm.sup.3. In other aspects, the density of
the first polyolefin may be from about 0.85 g/cm.sup.3to about 0.89
g/cm.sup.3, from about 0.85 g/cm.sup.3to about 0.88 g/cm.sup.3,
from about 0.84 g/cm.sup.3to about 0.88 g/cm.sup.3, or from about
0.83 g/cm.sup.3to about 0.87 g/cm.sup.3. In still other aspects,
the density is at about 0.84 g/cm.sup.3, about 0.85 g/cm.sup.3,
about 0.86 g/cm.sup.3, about 0.87 g/cm.sup.3, about 0.88
g/cm.sup.3, or about 0.89 g/cm.sup.3.
[0052] The percent crystallinity of the second polyolefin may be
less than about 60%, less than about 50%, less than about 40%, less
than about 35%, less than about 30%, less than about 25%, or less
than about 20%. The percent crystallinity may be at least about
10%. In some aspects, the crystallinity is in the range of from
about 2% to about 60%.
[0053] As noted, the silane-crosslinked polyolefin elastomers or
blends, e.g., as employed in membranes 10 (e.g., within the top and
bottom layers 14, 38 as shown in FIG. 1), membranes 10 configured
as roofing membranes, and similar structures comparable to top and
bottom layers 14, 38, includes both the first polyolefin and the
second polyolefin. The second polyolefin is generally used to
modify the hardness and/or processability of the first polyolefin
having a density less than 0.90 g/cm.sup.3. In some aspects, more
than just the first and second polyolefins may be used to form the
silane-crosslinked polyolefin elastomer or blend. For example, in
some aspects, one, two, three, four, or more different polyolefins
having a density less than 0.90 g/cm.sup.3, less than 0.89
g/cm.sup.3, less than 0.88 g/cm.sup.3, less than 0.87 g/cm.sup.3,
less than 0.86 g/cm.sup.3, or less than 0.85 g/cm.sup.3 may be
substituted and/or used for the first polyolefin. In some aspects,
one, two, three, four, or more different polyolefins,
polyethylene-co-propylene copolymers may be substituted and/or used
for the second polyolefin.
[0054] The blend of the first polyolefin having a density less than
0.90 g/cm.sup.3 and the second polyolefin having a crystallinity
less than 40% is used because the subsequent silane grafting and
crosslinking of these first and second polyolefin materials
together are what form the core resin structure in the final
silane-crosslinked polyolefin elastomer. Although additional
polyolefins may be added to the blend of the silane-grafted,
silane-crosslinkable, and/or silane-crosslinked polyolefin
elastomer as fillers to improve and/or modify the Young's modulus
as desired for the final product, any polyolefins added to the
blend having a crystallinity equal to or greater than 40% are not
chemically or covalently incorporated into the crosslinked
structure of the final silane-crosslinked polyolefin elastomer.
[0055] In some aspects, the first and second polyolefins may
further include one or more thermoplastic vulcanizates (TPVs)
and/or EPDM with or without silane graft moieties where the TPV
and/or EPDM polymers are present in an amount of up to 20 wt. % of
the silane-crosslinker polyolefin elastomer/blend.
Grafting Initiator
[0056] A grafting initiator (also referred to as "a radical
initiator" in the disclosure) can be utilized in the grafting
process of at least the first and second polyolefins by reacting
with the respective polyolefins to form a reactive species that can
react and/or couple with the silane crosslinker molecule. The
grafting initiator can include halogen molecules, azo compounds
(e.g., azobisisobutyl), carboxylic peroxyacids, peroxyesters,
peroxyketals, and peroxides (e.g., alkyl hydroperoxides, dialkyl
peroxides, and diacyl peroxides). In some embodiments, the grafting
initiator is an organic peroxide selected from di-t-butyl peroxide,
t-butyl cumyl peroxide, dicumyl peroxide,
2,5-dimethyl-2,5-di(t-butyl-peroxy)hexyne-3,
1,3-bis(t-butyl-peroxy-isopropyl)benzene,
n-butyl-4,4-bis(t-butyl-peroxy)valerate, benzoyl peroxide,
t-butylperoxybenzoate, t-butylperoxy isopropyl carbonate, and
t-butylperbenzoate, as well as bis(2-methylbenzoyl)peroxide,
bis(4-methylbenzoyl)peroxide, t-butyl peroctoate, cumene
hydroperoxide, methyl ethyl ketone peroxide, lauryl peroxide,
tert-butyl peracetate, di-t-amyl peroxide, t-amyl peroxybenzoate,
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
.alpha.,.alpha.'-bis(t-butylperoxy)-1,3-diisopropylbenzene,
.alpha.,.alpha.'-bis(t-butylpexoxy)-1,4-diisopropylbenzene,
2,5-bis(t-butylperoxy)-2,5-dimethylhexane, and
2,5-bis(t-butylperoxy)-2,5-dimethyl-3-hexyne and
2,4-dichlorobenzoyl peroxide. Exemplary peroxides include those
sold under the tradename LUPEROX.TM. (available from Arkema,
Inc.).
[0057] In some aspects, the grafting initiator is present in an
amount of from greater than 0 wt. % to about 2 wt. % of the
composition, including from about 0.15 wt. % to about 1.2 wt. % of
the composition. The amount of initiator and silane employed may
affect the final structure of the silane grafted polymer (e.g., the
degree of grafting in the grafted polymer and the degree of
crosslinking in the cured polymer). In some aspects, the reactive
composition contains at least 100 ppm of initiator, or at least 300
ppm of initiator. The initiator may be present in an amount from
300 ppm to 1500 ppm or from 300 ppm to 2000 ppm. The
silane:initiator weight ratio may be from about 20:1 to 400:1,
including from about 30:1 to about 400:1, from about 48:1 to about
350:1, and from about 55:1 to about 333:1.
[0058] The grafting reaction can be performed under conditions that
optimize grafts onto the interpolymer backbone while minimizing
side reactions (e.g., the homopolymerization of the grafting
agent). The grafting reaction may be performed in a melt, in
solution, in a solid-state, and/or in a swollen-state. The
silanation may be performed in a wide-variety of equipment (e.g.,
twin screw extruders, single screw extruders, Brabenders, internal
mixers such as Banbury mixers, and batch reactors). In some
embodiments, the polyolefin, silane, and initiator are mixed in the
first stage of an extruder. The melt temperature (i.e., the
temperature at which the polymer starts melting and begins to flow)
may be from about 120.degree. C. to about 260.degree. C., including
from about 130.degree. C. to about 250.degree. C.
Silane Crosslinker
[0059] A silane crosslinker can be used to covalently graft silane
moieties onto the first and second polyolefins and the silane
crosslinker may include alkoxysilanes, silazanes, siloxanes, or a
combination thereof. The grafting and/or coupling of the various
potential silane crosslinkers or silane crosslinker molecules is
facilitated by the reactive species formed by the grafting
initiator reacting with the respective silane crosslinker.
[0060] In some aspects, the silane crosslinker is a silazane where
the silazane may include, for example, hexamethyldisilazane (HMDS),
Bis(trimethylsilyl)amine, vinyltrimethoxysilane (VTMO) and/or
vinyltriethoxysilane (VTEO). In some aspects, the silane
crosslinker is a siloxane where the siloxane may include, for
example, polydimethylsiloxane (PDMS) and
octamethylcyclotetrasiloxane.
[0061] In some aspects, the silane crosslinker is an alkoxysilane.
As used herein, the term "alkoxysilane" refers to a compound that
comprises a silicon atom, at least one alkoxy group and at least
one other organic group, wherein the silicon atom is bonded with
the organic group by a covalent bond. Preferably, the alkoxysilane
is selected from alkylsilanes; acryl-based silanes; vinyl-based
silanes; aromatic silanes; epoxy-based silanes; amino-based silanes
and amines that possess --NH.sub.2, --NHCH.sub.3or
--N(CH.sub.3).sub.2; ureide-based silanes; mercapto-based silanes;
and alkoxysilanes which have a hydroxyl group (i.e., --OH). An
acryl-based silane may be selected from the group comprising
beta-acryloxyethyl trimethoxysilane; beta-acryloxy propyl
trimethoxysilane; gamma-acryloxyethyl trimethoxysilane;
gamma-acryloxypropyl trimethoxysilane; beta-acryloxyethyl
triethoxysilane; beta-acryloxypropyl triethoxysilane;
gamma-acryloxyethyl triethoxysilane; gamma-acryloxypropyl
triethoxysilane; beta-methacryloxyethyl trimethoxysilane;
beta-methacryloxypropyl trimethoxysilane; gamma-methacryloxyethyl
trimethoxysilane; gamma-methacryloxypropyl trimethoxysilane;
beta-methacryloxyethyl triethoxysilane; beta-methacryloxypropyl
triethoxysilane; gamma-methacryloxyethyl triethoxysilane;
gamma-methacryloxypropyl triethoxysilane;
3-methacryloxypropylmethyl diethoxysilane. A vinyl-based silane may
be selected from the group comprising vinyl trimethoxysilane; vinyl
triethoxysilane; p-styryl trimethoxysilane,
methylvinyldimethoxysilane, vinyldimethylmethoxysilane,
divinyldimethoxysilane, vinyltris(2-methoxyethoxy)silane, and
vinylbenzylethylenediaminopropyltrimethoxysilane. An aromatic
silane may be selected from phenyltrimethoxysilane and
phenyltriethoxysilane. An epoxy-based silane may be selected from
the group comprising 3-glycydoxypropyl trimethoxysilane;
3-glycydoxypropylmethyl diethoxysilane; 3-glycydoxypropyl
triethoxysilane; 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, and
glycidyloxypropylmethyldimethoxysilane. An amino-based silane may
be selected from the group comprising 3-aminopropyl
triethoxysilane; 3-aminopropyl trimethoxysilane;
3-aminopropyldimethyl ethoxysilane;
3-aminopropylmethyldiethoxysilane; 4-aminobutyltriethoxysilane;
3-aminopropyldiisopropyl ethoxysilane;
1-amino-2-(dimethylethoxysilyl)propane;
(aminoethylamino)-3-isobutyldimethyl methoxysilane;
N-(2-aminoethyl)-3-aminoisobutylmethyl dimethoxysilane;
(aminoethylaminomethyl)phenetyl trimethoxysilane;
N-(2-aminoethyl)-3-aminopropylmethyl dimethoxysilane;
N-(2-aminoethyl)-3-aminopropyl trimethoxysilane;
N-(2-aminoethyl)-3-aminopropyl triethoxysilane;
N-(6-aminohexyl)aminomethyl trimethoxysilane;
N-(6-aminohexyl)aminomethyl trimethoxysilane;
N-(6-aminohexyl)aminopropyl trimethoxysilane;
N-(2-aminoethyl)-1,1-aminoundecyl trimethoxysilane;
1,1-aminoundecyl triethoxysilane; 3-(m-aminophenoxy)propyl
trimethoxysilane; m-aminophenyl trimethoxysilane; p-aminophenyl
trimethoxysilane; (3-trimethoxysilylpropyl)diethylenetriamine;
N-methylaminopropylmethyl dimethoxysilane; N-methylaminopropyl
trimethoxysilane; dimethylaminomethyl ethoxysilane;
(N,N-dimethylaminopropyl)trimethoxysilane;
(N-acetylglycysil)-3-aminopropyl trimethoxysilane,
N-phenyl-3-aminopropyltrimethoxysilane,
N-phenyl-3-aminopropyltriethoxysilane,
phenylaminopropyltrimethoxysilane,
aminoethylaminopropyltrimethoxysilane, and
aminoethylaminopropylmethyldimethoxysilane. An ureide-based silane
may be 3-ureidepropyl triethoxysilane. A mercapto-based silane may
be selected from the group comprising 3-mercaptopropylmethyl
dimethoxysilane, 3-mercaptopropyl trimethoxysilane, and
3-mercaptopropyl triethoxysilane. An alkoxysilane having a hydroxyl
group may be selected from the group comprising hydroxymethyl
triethoxysilane; N-(hydroxyethyl)-N-methylaminopropyl
trimethoxysilane; bis(2-hydroxyethyl)-3-aminopropyl
triethoxysilane; N-(3-triethoxysilylpropyl)-4-hydroxy butylamide;
1,1-(triethoxysilyl)undecanol; triethoxysilyl undecanol; ethylene
glycol acetal; and N-(3-ethoxysilylpropyl)gluconamide.
[0062] In some aspects, the alkylsilane may be expressed with a
general formula: R.sub.nSi(OR').sub.4-n wherein: n is 1, 2 or 3; R
is a C.sub.1-20alkyl or a C.sub.2-20alkenyl; and R' is an
C.sub.1-20alkyl. The term "alkyl" by itself or as part of another
substituent, refers to a straight, branched or cyclic saturated
hydrocarbon group joined by single carbon-carbon bonds having 1 to
20 carbon atoms, for example 1 to 10 carbon atoms, for example 1 to
8 carbon atoms, preferably 1 to 6 carbon atoms. When a subscript is
used herein following a carbon atom, the subscript refers to the
number of carbon atoms that the named group may contain. Thus, for
example, C.sub.1-6alkyl means an alkyl of one to six carbon atoms.
Examples of alkyl groups are methyl, ethyl, propyl, isopropyl,
butyl, isobutyl, sec-butyl, f-butyl, 2-methylbutyl, pentyl,
iso-amyl and its isomers, hexyl and its isomers, heptyl and its
isomers, octyl and its isomer, decyl and its isomer, dodecyl and
its isomers. The term "C.sub.2-20alkenyl" by itself or as part of
another substituent, refers to an unsaturated hydrocarbyl group,
which may be linear, or branched, comprising one or more
carbon-carbon double bonds having 2 to 20 carbon atoms. Examples of
C.sub.2-6 alkenyl groups are ethenyl, 2-propenyl, 2-butenyl,
3-butenyl, 2-pentenyl and its isomers, 2-hexenyl and its isomers,
2,4-pentadienyl and the like.
[0063] In some aspects, the alkylsilane may be selected from the
group comprising methyltrimethoxysilane; methyltriethoxysilane;
ethyltrimethoxysilane; ethyltriethoxysilane;
propyltrimethoxysilane; propyltriethoxysilane;
hexyltrimethoxysilane; hexyltriethoxysilane; octyltrimethoxysilane;
octyltriethoxysilane; decyltrimethoxysilane; decyltriethoxysilane;
dodecyltrimethoxysilane: dodecyltriethoxysilane;
tridecyltrimethoxysilane; dodecyltriethoxysilane;
hexadecyltrimethoxysilane; hexadecyltriethoxysilane;
octadecyltrimethoxysilane; octadecyltriethoxysilane,
trimethylmethoxysilane, methylhydrodimethoxysilane,
dimethyldimethoxysilane, diisopropyldimethoxysilane,
diisobutyldimethoxysilane, isobutyltrimethoxysilane,
n-butyltrimethoxysilane, n-butylmethyldimethoxysilane,
phenyltrimethoxysilane, phenyltrimethoxysilane,
phenylmethyldimethoxysilane, triphenylsilanol,
n-hexyltrimethoxysilane, n-octyltrimethoxysilane,
isooctyltrimethoxysilane, decyltrimethoxysilane,
hexadecyltrimethoxysilane, cyclohexylmethyldimethoxysilane,
cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane,
tert-butylethyldimethoxysilane, tert-butylpropyldimethoxysilane,
dicyclohexyldimethoxysilane, and a combination thereof.
[0064] In some aspects, the alkylsilane compound may be selected
from triethoxyoctylsilane, trimethoxyoctylsilane, and a combination
thereof.
[0065] Additional examples of silanes that can be used as silane
crosslinkers include, but are not limited to, those of the general
formula
CH.sub.2.dbd.CR--(COO).sub.x(C.sub.xH.sub.2n).sub.ySiR'.sub.3,
wherein R is a hydrogen atom or methyl group; x is 0 or 1; y is 0
or 1; n is an integer from 1 to 12; each R' can be an organic group
and may be independently selected from an alkoxy group having from
1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), aryloxy group
(e.g., phenoxy), araloxy group (e.g., benzyloxy), aliphatic acyloxy
group having from 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy,
propanoyloxy), amino or substituted amino groups (e.g., alkylamino,
arylamino), or a lower alkyl group having 1 to 6 carbon atoms. x
and y may both equal 1. In some aspects, no more than one of the
three R' groups is an alkyl. In other aspects, not more than two of
the three R' groups is an alkyl.
[0066] Any silane, or mixture of silanes, known in the art that can
effectively graft to and crosslink an olefin polymer can be used in
the practice of the present disclosure. In some aspects, the silane
crosslinker can include, but is not limited to, unsaturated silanes
which include an ethylenically unsaturated hydrocarbyl group (e.g.,
a vinyl, allyl, isopropenyl, butenyl, cyclohexenyl or a
gamma-(meth)acryloxy allyl group) and a hydrolyzable group (e.g., a
hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group).
Non-limiting examples of hydrolyzable groups include, but are not
limited to, methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, and
alkyl, or arylamino groups. In other aspects, the silane
crosslinkers are unsaturated alkoxy silanes which can be grafted
onto the polymer. In still other aspects, additional exemplary
silane crosslinkers include vinyltrimethoxysilane (VTMO),
vinyltriethoxysilane (VTEO), 3-(trimethoxysilyl)propyl methacrylate
gamma-(meth)acryloxypropyl trimethoxysilane), and mixtures
thereof.
[0067] The silane crosslinker may be present in the silane-grafted
polyolefin elastomer in an amount of from greater than 0 wt. % to
about 10 wt. %, including from about 0.5 wt. % to about 5 wt. %.
The amount of silane crosslinker may be varied based on the nature
of the olefin polymer, the silane itself, the processing
conditions, the grafting efficiency, the application, and other
factors. The amount of silane crosslinker may be at least 2 wt. %,
including at least 4 wt. % or at least 5 wt. %, based on the weight
of the reactive composition. In other aspects, the amount of silane
crosslinker may be at least 10 wt. %, based on the weight of the
reactive composition. In still other aspects, the silane
crosslinker content is at least 1% based on the weight of the
reactive composition. In some embodiments, the silane crosslinker
fed to the extruder may include from about 0.5 wt. % to about 10
wt. % of silane monomer, from about 1 wt. % to about 5 wt. % silane
monomer, or from about 2 wt. % to about 4 wt. % silane monomer.
Condensation Catalyst
[0068] A condensation catalyst can facilitate both the hydrolysis
and subsequent condensation of the silane grafts on the
silane-grafted polyolefin elastomer to form crosslinks. In some
aspects, the crosslinking can be aided by the use of an electron
beam radiation. In some aspects, the condensation catalyst can
include, for example, organic bases, carboxylic acids, and
organometallic compounds (e.g., organic titanates and complexes or
carboxylates of lead, cobalt, iron, nickel, zinc, and tin (e.g., an
organo-tin catalyst)). In other aspects, the condensation catalyst
can include fatty acids and metal complex compounds such as metal
carboxylates; aluminum triacetyl acetonate, iron triacetyl
acetonate, manganese tetraacetyl acetonate, nickel tetraacetyl
acetonate, chromium hexaacetyl acetonate, titanium tetraacetyl
acetonate and cobalt tetraacetyl acetonate; metal alkoxides such as
aluminum ethoxide, aluminum propoxide, aluminum butoxide, titanium
ethoxide, titanium propoxide and titanium butoxide; metal salt
compounds such as sodium acetate, tin octylate, lead octylate,
cobalt octylate, zinc octylate, calcium octylate, lead naphthenate,
cobalt naphthenate, dibutyltin dioctoate, dibutyltin dilaurate,
dibutyltin maleate and dibutyltin di(2-ethylhexanoate); acidic
compounds such as formic acid, acetic acid, propionic acid,
p-toluenesulfonic acid, trichloroacetic acid, phosphoric acid,
monoalkylphosphoric acid, dialkylphosphoric acid, phosphate ester
of p-hydroxyethyl (meth)acrylate, monoalkylphosphorous acid and
dialkylphosphorous acid; acids such as p-toluenesulfonic acid,
phthalic anhydride, benzoic acid, benzenesulfonic acid,
dodecylbenzenesulfonic acid, formic acid, acetic acid, itaconic
acid, oxalic acid and maleic acid, ammonium salts, lower amine
salts or polyvalent metal salts of these acids, sodium hydroxide,
lithium chloride; organometal compounds such as diethyl zinc and
tetra(n-butoxy)titanium; and amines such as dicyclohexylamine,
triethylamine, N,N-dimethylbenzylamine, N,N,N',N'-tetramethyl-1,3-
butanediamine, diethanolamine, triethanolamine and
cyclohexylethylamine. In still other aspects, the condensation
catalyst can include ibutyltindilaurate, dioctyltinmaleate,
dibutyltindiacetate, dibutyltindioctoate, ethylene butyl acrylate
copolymer (e.g., LOTRYL.RTM. 17BA07 from Arkema Functional
Polyolefins, and LUCOFIN.RTM. 1400MN from Lucobit AG), stannous
acetate, stannous octoate, lead naphthenate, zinc caprylate, and
cobalt naphthenate. Depending on the desired final material
properties of the silane-crosslinked polyolefin elastomer or blend,
a single condensation catalyst or a mixture of condensation
catalysts may be utilized. The condensation catalyst(s) may be
present in an amount of from about 0.01 wt. % to about 1.0 wt. %,
including from about 0.25 wt. % to about 8 wt. %, based on the
total weight of the silane-grafted polyolefin elastomer/blend
composition.
[0069] In some aspects, a crosslinking system can include and use
one or all of a combination of radiation, heat, moisture, and
additional condensation catalyst. In some aspects, the condensation
catalyst may be present in an amount of from 0.25 wt. % to 8 wt. %.
In other aspects, the condensation catalyst may be included in an
amount of from about 1 wt. % to about 10 wt. % or from about 2 wt.
% to about 5 wt. %.
Optional Additional Components
[0070] The silane-crosslinked polyolefin elastomer may optionally
include one or more fillers. The filler(s) may be extruded with the
silane-grafted polyolefin and in some aspects may include
additional polyolefins having a crystallinity greater than 20%,
greater than 30%, greater than 40%, or greater than 50%. In some
aspects, the filler(s) may include metal oxides, metal hydroxides,
metal carbonates, metal sulfates, metal silicates, clays, talcs,
carbon black, and silicas. Depending on the application and/or
desired properties, these materials may be fumed or calcined.
Further, in some implementations, a filler added to the
silane-crosslinked polyolefin elastomer can include one or more
coatings, e.g., an organic coating such as stearic acid, a
silane-based material, etc.
[0071] With further regard to metal-containing fillers, the metal
of the metal oxide, metal hydroxide, metal carbonate, metal
sulfate, or metal silicate may be selected from alkali metals
(e.g., lithium, sodium, potassium, rubidium, cesium, and francium);
alkaline earth metals (e.g., beryllium, magnesium, calcium,
strontium, barium, and radium); transition metals (e.g., zinc,
molybdenum, cadmium, scandium, titanium (e.g., organic-coated
titanium dioxide), vanadium, chromium, manganese, iron, cobalt,
nickel, copper, yttrium, zirconium, niobium, technetium, ruthenium,
rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium,
osmium, indium, platinum, gold, mercury, rutherfordium, dubnium,
seaborgium, bohrium, hassium, and copernicium); post-transition
metals (e.g., aluminum, gallium, indium, tin, thallium, lead,
bismuth, and polonium); lanthanides (e.g., lanthanum, cerium,
praseodymium, neodymium, promethium, samarium, europium,
gadolinium, terbium, dysprosium, holmium, erbium, thulium,
ytterbium, and lutetium); actinides (e.g., actinium, thorium,
protactinium, uranium, neptunium, plutonium, americium, curium,
berkelium, californium, einsteinium, fermium, mendelevium,
nobelium, and lawrencium); germanium; arsenic; antimony; and
astatine.
[0072] The filler(s) of the silane-crosslinked polyolefin elastomer
or blend may be present in an amount of from greater than 0 wt. %
to about 50 wt. %, including from about 1 wt. % to about 20 wt. %,
and from about 3 wt. % to about 10 wt. %.
[0073] The silane-crosslinked polyolefin elastomer and/or the
respective articles formed (e.g., a membrane 10 as depicted in FIG.
1) may also include waxes (e.g., paraffin waxes, microcrystalline
waxes, HDPE waxes, LDPE waxes, thermally degraded waxes, byproduct
polyethylene waxes, optionally oxidized Fischer-Tropsch waxes,
organic siloxane-based waxes (e.g., TEGOPRENE.RTM. pellets) and
functionalized waxes). In some embodiments, the wax(es) are present
in an amount of from about 0 wt. % to about 10 wt. %.
[0074] Tackifying resins (e.g., aliphatic hydrocarbons, aromatic
hydrocarbons, modified hydrocarbons, terpens, modified terpenes,
hydrogenated terpenes, rosins, rosin derivatives, hydrogenated
rosins, and mixtures thereof) may also be included in the
silane-crosslinker polyolefin elastomer/blend. The tackifying
resins may have a ring and ball softening point in the range of
from 70.degree. C. to about 150.degree. C. and a viscosity of less
than about 3,000 cP at 177.degree. C. In some aspects, the
tackifying resin(s) are present in an amount of from about 0 wt. %
to about 10 wt. %.
[0075] In some aspects, the silane-crosslinker polyolefin elastomer
may include one or more oils. Non-limiting types of oils include
white mineral oils and naphthenic oils. In some embodiments, the
oil(s) are present in an amount of from about 0 wt. % to about 10
wt. %.
[0076] In some aspects, the silane-crosslinked polyolefin elastomer
may include one or more filler polyolefins having a crystallinity
greater than 20%, greater than 30%, greater than 40%, or greater
than 50%. The filler polyolefin may include polypropylene,
poly(ethylene-co-propylene), and/or other ethylene/.alpha.-olefin
copolymers. In some aspects, the use of the filler polyolefin may
be present in an amount of from about 5 wt. % to about 60 wt. %,
from about 10 wt. % to about 50 wt. %, from about 20 wt. % to about
40 wt. %, or from about 5 wt. % to about 20 wt. %. The addition of
the filler polyolefin may increase the Young's modulus by at least
10%, by at least 25%, or by at least 50% for the final
silane-crosslinked polyolefin elastomer.
[0077] In some aspects, the silane-crosslinker polyolefin elastomer
of the present disclosure may include one or more stabilizers
(e.g., metal deactivators and antioxidants, including IRGANOX.RTM.
sterically hindered phenolic antioxidants; IRGAFOS.RTM. phosphite
stabilizers; IRGASTAB.RTM. non-phenolic, phosphite stabilizers;
HYCITE.RTM. inorganic stabilizer and acid scavenger, and others).
The silane-crosslinked polyolefin elastomer may be treated before
grafting, after grafting, before crosslinking, and/or after
crosslinking. Other additives may also be included. Non-limiting
examples of additives include antistatic agents, dyes, pigments, UV
light absorbers (e.g., high molecular weight hindered amines such
as CHIMASSORB.RTM. and TINUVIN.RTM. hindered amines from BASF
Corp.), nucleating agents, fillers (e.g., high molecular weight
silicone such as GENIOPLAST.RTM. pellets from Wacker Chemie AG),
glass fibers, slip agents, plasticizers, fire retardants,
lubricants, processing aides, smoke inhibitors, anti-blocking
agents, acid scavengers, and viscosity control agents. The
antioxidant(s) may be present in an amount of less than 0.5 wt. %,
including less than 0.2 wt. % of the composition.
[0078] In some aspects, titanium dioxide, a white pigment, may be
added to the formulation to provide opacity and color. In addition,
the titanium dioxide (e.g., KRONOS.RTM. TiO.sub.2 from Kronos Int'l
Inc.) also may provide ultraviolet light protection. In some
aspects, the titanium dioxide may be pre-blended with the first
and/or second polyolefins (of the type set forth above) to ensure
complete dispersal of the titanium dioxide throughout the
composition. In some aspects, to ensure complete dispersal of the
titanium dioxide into the composition prior to extrusion or other
formation techniques, the titanium dioxide may be pre-blended with
the first and/or second polyolefins in an amount up to 30 wt. %, up
to 20 wt. %, or up to 10 wt. %.
Method for Making the Silane-Grafted Polyolefin Elastomer
[0079] The synthesis/production of the silane-crosslinked
polyolefin elastomer (e.g., as employed in the top and bottom
layers 14, 38 of the membrane 10, a membrane 10 configured for a
roofing membrane, or other comparable structure) may be performed
by combining the respective components in one extruder using a
single-step Monosil process or in two extruders using a two-step
Sioplas process, which eliminates the need for additional steps of
mixing and shipping rubber compounds prior to extrusion.
[0080] Referring now to FIG. 2, the general chemical process used
during both the single-step Monosil process and two-step Sioplas
process used to synthesize the silane-crosslinked polyolefin
elastomer is provided. The process starts with a grafting step that
includes initiation from a grafting initiator followed by
propagation and chain transfer with the first and second
polyolefins. The grafting initiator, in some aspects a peroxide or
azo compound, homolytically cleaves to form two radical initiator
fragments that transfer to one of the first and second polyolefins
chains through a propagation step. The free radical, now positioned
on the first or second polyolefin chain, can then transfer to a
silane molecule and/or another polyolefin chain. Once the initiator
and free radicals are consumed, the silane grafting reaction for
the first and second polyolefins is complete.
[0081] Still referring to FIG. 2, once the silane grafting reaction
is complete, a mixture of stable first and second silane-grafted
polyolefins is produced. A crosslinking catalyst may then be added
to the first and second silane-grafted polyolefins to form the
silane-grafted polyolefin elastomer. The crosslinking catalyst may
first facilitate the hydrolysis of the silyl group grafted onto the
polyolefin backbones to form reactive silanol groups. The silanol
groups may then react with other silanol groups on other polyolefin
molecules to form a crosslinked network of elastomeric polyolefin
polymer chains linked together through siloxane linkages. The
density of silane crosslinks throughout the silane-grafted
polyolefin elastomer can influence the material properties
exhibited by the elastomer.
[0082] Referring now to FIGS. 3 and 4A, a method 200 for making the
membrane 10, particularly the top and bottom layers 14 and 38,
using the two-step Sioplas process is shown. The method 200 may
begin with a step 204 that includes extruding (e.g., with a twin
screw extruder 252) a first polyolefin 240 having a density less
than 0.90 g/cm.sup.3, a second polyolefin 244, and a silan cocktail
248 including the silane crosslinker (e.g., vinyltrimethoxy silane
(VTMO), vinlytriethoxy silane (VTEO), etc.) and the grafting
initiator (e.g. dicumyl peroxide) together to form a silane-grafted
polyolefin blend. The first polyolefin 240 and second polyolefin
244 may be added to a reactive twin screw extruder 252 using an
addition hopper 256. The silan cocktail 248 may also be added to
the twin screws 260 further down the extrusion line to help promote
better mixing with the blend of the first and second polyolefins
240, 244. A forced volatile organic compound (VOC) vacuum 264 may
be used on the reactive twin screw extruder 252 to help maintain a
desired reaction pressure. The twin screw extruder 252 is
considered reactive because the radical initiator and silane
crosslinker are reacting with and forming new covalent bonds with
both the first and second polyolefins 240, 244. The melted
silane-grafted polyolefin blend can exit the reactive twin screw
extruder 252 using a gear pump 268 that injects the molten
silane-grafted polyolefin blend into a water pelletizer 272 that
can form a pelletized silane-grafted polyolefin blend 276. In some
aspects, the molten silane-grafted polyolefin blend 276 may be
extruded into pellets, pillows, or any other configuration prior to
the incorporation of the condensation catalyst 280 (see FIG. 4B)
and formation of the final article (e.g., a membrane 10 as depicted
in FIG. 1).
[0083] The reactive twin screw extruder 252 can be configured to
have a plurality of different temperature zones (e.g., Z0-Z12 as
shown in FIG. 4A) that extend for various lengths of the twin screw
extruder 252. In some aspects, the respective temperature zones may
have temperatures ranging from about room temperature to about
180.degree. C., from about 120.degree. C. to about 170.degree. C.,
from about 120.degree. C. to about 160.degree. C., from about
120.degree. C. to about 150.degree. C., from about 120.degree. C.
to about 140.degree. C., from about 120.degree. C. to about
130.degree. C., from about 130.degree. C. to about 170.degree. C.,
from about 130.degree. C. to about 160.degree. C., from about
130.degree. C. to about 150.degree. C., from about 130.degree. C.
to about 140.degree. C., from about 140.degree. C. to about
170.degree. C., from about 140.degree. C. to about 160.degree. C.,
from about 140.degree. C. to about 150.degree. C., from about
150.degree. C. to about 170.degree. C., and from about 150.degree.
C. to about 160.degree. C. In some aspects, Z0 may have a
temperature from about 60.degree. C. to about 110.degree. C. or no
cooling; Z1 may have a temperature from about 120.degree. C. to
about 130.degree. C.; Z2 may have a temperature from about
140.degree. C. to about 150.degree. C.; Z3 may have a temperature
from about 150.degree. C. to about 160.degree. C.; Z4 may have a
temperature from about 150.degree. C. to about 160.degree. C.; Z5
may have a temperature from about 150.degree. C. to about
160.degree. C.; Z6 may have a temperature from about 150.degree. C.
to about 160.degree. C.; Z7 may have a temperature from about
150.degree. C. to about 160.degree. C.; and Z8-Z12 may have a
temperature from about 150.degree. C. to about 160.degree. C.
[0084] In some aspects, the number average molecular weight of the
silane-grafted polyolefin elastomers may be in the range of from
about 4,000 g/mol to about 30,000 g/mol, including from about 5,000
g/mol to about 25,000 g/mol and from about 6,000 g/mol to about
14,000 g/mol. The weight average molecular weight of the grafted
polymers may be from about 8,000 g/mol to about 60,000 g/mol,
including from about 10,000 g/mol to about 30,000 g/mol.
[0085] Referring now to FIGS. 3 and 4B, the method 200 next
includes a step 208 of extruding the silane-grafted polyolefin
blend 276 and the condensation catalyst 280 together to form a
silane-crosslinkable polyolefin blend 298. In some aspects, one or
more optional additives 284 may be added with the silane-grafted
polyolefin blend 276 and the condensation catalyst 280 to adjust
the final material properties of the silane-crosslinkable
polyolefin blend 298. In step 208, the silane-grafted polyolefin
blend 276 is mixed with a silanol forming condensation catalyst 280
to form reactive silanol groups on the silane grafts that can
subsequently crosslink when exposed to humidity and/or heat. In
some aspects, the condensation catalyst 280 can include a mixture
of sulfonic acid, antioxidant, process aide, and carbon black for
coloring where the ambient moisture is sufficient for this
condensation catalyst 280 to crosslink the silane-crosslinkable
polyolefin blend 298 over a longer time period (e.g., about 48
hours). The silane-grafted polyolefin blend 276 and the
condensation catalyst 280 may be added to a reactive single screw
extruder 288 using an addition hopper (similar to addition hopper
256 shown in FIG. 4A) and an addition gear pump 296. The
combination of the silane-grafted polyolefin blend 276 and the
condensation catalyst 280, and in some aspects one or more optional
additives 284, may be added to a single screw 292 of the reactive
single screw extruder 288. The single screw extruder 288 is
considered reactive because the silane-grafted polyolefin blend 276
and the condensation catalyst 280 are melted and combined together
to mix the condensation catalyst 280 thoroughly and evenly
throughout the melted silane-grafted polyolefin blend 276. The
melted silane-crosslinkable polyolefin blend 298, as formed in step
208, can exit the reactive single screw extruder 288 through a die
that can inject the molten silane-crosslinkable polyolefin blend
298 into the form of an uncured membrane element.
[0086] During step 208, as the silane-grafted polyolefin blend 276
is extruded together with the condensation catalyst 280 to form the
silane-crosslinkable polyolefin blend 298, a certain amount of
crosslinking may occur. In some aspects, the silane-crosslinkable
polyolefin blend 298 may be about 25% cured, about 30% cured, about
35% cured, about 40% cured, about 45% cured, about 50% cured, about
55% cured, about 60% cured, bout 65% cured, or about 70% cured,
where a gel test (ASTM D2765) can be used to determine the amount
of crosslinking in the final silane-crosslinked polyolefin
elastomer.
[0087] Referring to FIGS. 3 and 4B, the method 200 further includes
a step 212 of extruding and/or calendaring the silane-crosslinkable
polyolefin elastomer or blend 298 to form the top and bottom layers
14, 38 of a membrane 10 (or a single membrane of comparable
structure), as comprising the uncured silane-crosslinkable
polyolefin elastomer. The silane-crosslinkable polyolefin elastomer
or blend 298 is in a melted or molten state where it can flow and
be shaped as it exits the reactive single screw extruder 288. A
calendar system 302 is a device having two or more rollers (the
area between the rollers is called a nip) used to process the
melted silane-crosslinkable polyolefin elastomer blend 298 into a
sheet, layer, or membrane. As the melted silane-crosslinkable
polyolefin elastomer blend 298 leaves the reactive single screw
extruder 288, it forms a pool of silane-crosslinkable polyolefin
elastomer 306 at a first nip point of the calendar system 302. The
pool of silane-crosslinkable polyolefin elastomer 306 is then
pressed or rolled into the top or bottom layer 14, 38 respectively.
The scrim layer 26 may be added to the top or bottom layer 14, 38,
respectively, at any point during the calendaring process using a
scrim roll 318. The scrim layer 26, as coupled to the top or bottom
layer 14, 38, forms a partial scrim membrane 322. The partial scrim
membrane 322 may be further calendared and pressed with the
respectively missing top or bottom layer 14, 38 to form the uncured
membrane element.
[0088] Referring again to FIG. 3, the method 200 can further
include a step 216 of crosslinking the silane-crosslinkable
polyolefin blend 298 of the membrane element in an uncured form at
an ambient temperature and/or an ambient humidity to form the top
and bottom layers 14, 38 of the membrane 10 (see FIG. 1) having a
density from about 0.80 g/cm.sup.3 to about 1.75 g/cm.sup.3, or a
membrane comparable to either of these layers. More particularly,
in this crosslinking process, the water hydrolyzes the silane of
the silane-crosslinkable polyolefin elastomer to produce a silanol.
The silanol groups on various silane grafts can then be condensed
to form intermolecular, irreversible Si--O--Si crosslink sites. The
amount of crosslinked silane groups, and thus the final polymer
properties, can be regulated by controlling the production process,
including the amount of catalyst used.
[0089] The crosslinking/curing of step 216 of the method 200 (see
FIG. 3) may occur over a time period of from greater than 0 to
about 20 hours. In some aspects, curing takes place over a time
period of from about 1 hour to about 20 hours, 10 hours to about 20
hours, from about 15 hours to about 20 hours, from about 5 hours to
about 15 hours, from about 1 hour to about 8 hours, or from about 3
hours to about 6 hours. The temperature during the
crosslinking/curing may be about room temperature, from about
20.degree. C. to about 25.degree. C., from about 20.degree. C. to
about 150.degree. C., from about 25.degree. C. to about 100.degree.
C., or from about 20.degree. C. to about 75.degree. C. The humidity
during curing may be from about 30% to about 100%, from about 40%
to about 100%, or from about 50% to about 100%.
[0090] In some aspects, an extruder setting is used that is capable
of extruding thermoplastic, with long L/D, 30 to 1, at an extruder
heat setting close to thermoplastic vulcanizates (TPV) processing
conditions wherein the extrudate crosslinks at ambient conditions
becoming a thermoset in properties. In other aspects, this process
may be accelerated by steam exposure. Immediately after extrusion,
the gel content (also called the crosslink density) may be about
60%, but after 96 hrs at ambient conditions, the gel content may
reach greater than about 95%.
[0091] In some aspects, one or more reactive single screw extruders
288 may be used to form the uncured membrane element (and
corresponding single ply membrane 10) that has one or more types of
silane-crosslinked polyolefin elastomers. For example, in some
aspects, one reactive single screw extruder 288 may be used to
produce and extrude a first silane-crosslinked polyolefin elastomer
employed in a top layer 14 of a membrane 10 (see FIG. 1), while a
second reactive single screw extruder 288 may be used to produce
and extrude a second silane-crosslinked polyolefin elastomer
employed in a bottom layer 38 of the membrane 10. The complexity,
architecture and property requirements of the membrane 10, e.g., as
configured for a roofing membrane, will determine the number and
types of reactive single screw extruder 288 necessary to fabricate
it. Similarly, the one or more reactive single screw extruders 288
can be employed to form one or more membranes or other structures
comparable to the top and bottom layers 14, 38 of the membrane
10.
[0092] It is understood that the prior description outlining and
teaching the various membranes 10, and their respective components
and compositions, can be used in any combination, and applies
equally well to the method 200 for making the membrane 10 using the
two-step Sioplas process as shown in FIGS. 3, 4A and 4B.
[0093] Referring now to FIGS. 5 and 6, a method 400 for making the
membrane 10 using the one-step Monosil process is shown. The method
400 may begin with a step 404 that includes extruding (e.g., with a
single screw extruder 444) the first polyolefin 240 having a
density less than 0.90 g/cm.sup.3, the second polyolefin 244, the
silan cocktail 248 including the silane crosslinker (e.g.,
vinyltrimethoxy silane, VTMO) and grafting initiator (e.g. dicumyl
peroxide), and the condensation catalyst 280 together to form the
crosslinkable silane-grafted polyolefin blend 298. The first
polyolefin 240, second polyolefin 244, and silan cocktail 248 may
be added to the reactive single screw extruder 444 using an
addition hopper 440. In some aspects, the silan cocktail 248 may be
added to a single screw 448 further down the extrusion line to help
promote better mixing with the first and second polyolefin 240, 244
blend. In some aspects, one or more optional additives 284 may be
added with the first polyolefin 240, second polyolefin 244,
condensation catalyst 280 and silan cocktail 248 to adjust the
final material properties of the silane-crosslinkable polyolefin
blend 298. The single screw extruder 444 is considered reactive
because the grafting initiator and silane crosslinker of the silan
cocktail 248 are reacting with and forming new covalent bonds with
both the first and second polyolefins 240, 244. In addition, the
reactive single screw extruder 444 mixes the condensation catalyst
280 in together with the melted silane-grafted polyolefin blend
comprising the first and second polyolefins 240, 244, silan
cocktail 248 and any optional additives 284. The resulting melted
silane-crosslinkable polyolefin blend 298 can exit the reactive
single screw extruder 444 using a gear pump (not shown) and/or die
that can eject the molten silane-crosslinkable polyolefin blend 298
into the form of an uncured membrane element.
[0094] During step 404, as the first polyolefin 240, second
polyolefin 244, silan cocktail 248, and condensation catalyst 280
are extruded together, a certain amount of crosslinking may occur
in the reactive single screw extruder 444 to the
silane-crosslinkable blend 298. In some aspects, the
silane-crosslinkable polyolefin blend 298 may be about 25% cured,
about 30% cured, about 35% cured, about 40% cured, about 45% cured,
about 50% cured, about 55% cured, about 60% cured, bout 65% cured,
or about 70% as it leaves the reactive single screw extruder 444.
The gel test (ASTM D2765) can be used to determine the amount of
crosslinking in the final silane-crosslinked polyolefin
elastomer.
[0095] The reactive single screw extruder 444 can be configured to
have a plurality of different temperature zones (e.g., Z0-Z7 as
shown in FIG. 6) that extend for various lengths along the
extruder. In some aspects, the respective temperature zones may
have temperatures ranging from about room temperature to about
180.degree. C., from about 120.degree. C. to about 170.degree. C.,
from about 120.degree. C. to about 160.degree. C., from about
120.degree. C. to about 150.degree. C., from about 120.degree. C.
to about 140.degree. C., from about 120.degree. C. to about
130.degree. C., from about 130.degree. C. to about 170.degree. C.,
from about 130.degree. C. to about 160.degree. C., from about
130.degree. C. to about 150.degree. C., from about 130.degree. C.
to about 140.degree. C., from about 140.degree. C. to about
170.degree. C., from about 140.degree. C. to about 160.degree. C.,
from about 140.degree. C. to about 150.degree. C., from about
150.degree. C. to about 170.degree. C., and from about 150.degree.
C. to about 160.degree. C. In some aspects, Z0 may have a
temperature from about 60.degree. C. to about 110.degree. C. or no
cooling; Z1 may have a temperature from about 120.degree. C. to
about 130.degree. C.; Z2 may have a temperature from about
140.degree. C. to about 150.degree. C.; Z3 may have a temperature
from about 150.degree. C. to about 160.degree. C.; Z4 may have a
temperature from about 150.degree. C. to about 160.degree. C.; Z5
may have a temperature from about 150.degree. C. to about
160.degree. C.; Z6 may have a temperature from about 150.degree. C.
to about 160.degree. C.; and Z7 may have a temperature from about
150.degree. C. to about 160.degree. C.
[0096] In some aspects, the number average molecular weight of the
silane-grafted polyolefin elastomers may be in the range of from
about 4,000 g/mol to about 30,000 g/mol, including from about 5,000
g/mol to about 25,000 g/mol and from about 6,000 g/mol to about
14,000 g/mol. The weight average molecular weight of the grafted
polymers may be from about 8,000 g/mol to about 60,000 g/mol,
including from about 10,000 g/mol to about 30,000 g/mol.
[0097] Referring to FIGS. 5 and 6, the method 400 further includes
a step 408 of extruding and/or calendaring the silane-crosslinkable
polyolefin elastomer or blend 298 to form the top and bottom layers
14, 38, as comprising the uncured silane-crosslinkable polyolefin
elastomer. The silane-crosslinkable polyolefin elastomer or blend
298 is in a melted or molten state where it can flow and be shaped
as it exits the reactive single screw extruder 444. As previously
mentioned, the calendar system 302 is a device having two or more
rollers (the area between the rollers is called a nip) used to
process the melted silane-crosslinkable polyolefin elastomer blend
298 into a sheet, layer or membrane. As the melted
silane-crosslinkable polyolefin elastomer blend 298 leaves the
reactive single screw extruder 444, it forms a pool of
silane-crosslinkable polyolefin elastomer 306 at a first nip point
of the calendar system 302. The pool of silane-crosslinkable
polyolefin elastomer 306 is then pressed or rolled into the top or
bottom layer 14, 38, respectively. The scrim layer 26 may be added
to the top or bottom layer 14, 38 respectively at any point during
the calendaring process using a scrim roll 318. The scrim layer 26,
as coupled to the top or bottom layer 14, 38, forms a partial scrim
membrane 322. The partial scrim membrane 322 may be further
calendared and pressed with the respectively missing top or bottom
layer 14, 38 to form an uncured membrane element.
[0098] Still referring to FIG. 5, the method 400 can further
include a step 412 of crosslinking the silane-crosslinkable
polyolefin blend 298 of the uncured membrane element at an ambient
temperature and an ambient humidity to form the element into the
membrane 10 (see FIG. 1) having a density from about 0.80
g/cm.sup.3 to about 1.75 g/cm.sup.3. The amount of crosslinked
silane groups, and thus the final polymer properties of the
membrane 10, can be regulated by controlling the production
process, including the amount of catalyst used.
[0099] The step 412 of crosslinking the silane-crosslinkable
polyolefin blend 298 may occur over a time period of from greater
than 0 to about 20 hours. In some aspects, curing takes place over
a time period of from about 1 hour to about 20 hours, 10 hours to
about 20 hours, from about 15 hours to about 20 hours, from about 5
hours to about 15 hours, from about 1 hour to about 8 hours, or
from about 3 hours to about 6 hours. The temperature during the
crosslinking and curing may be about room temperature, from about
20.degree. C. to about 25.degree. C., from about 20.degree. C. to
about 150.degree. C., from about 25.degree. C. to about 100.degree.
C., or from about 20.degree. C. to about 75.degree. C. The humidity
during curing may be from about 30% to about 100%, from about 40%
to about 100%, or from about 50% to about 100%.
[0100] In some aspects, an extruder setting is used that is capable
of extruding thermoplastic, with long LID, 30 to 1, at an extruder
heat setting close to TPV processing conditions wherein the
extrudate crosslinks at ambient conditions becoming a thermoset in
properties. In other aspects, this process may be accelerated by
steam exposure. Immediately after extrusion, the gel content (also
called the crosslink density) may be about 60%, but after 96 hrs at
ambient conditions, the gel content may reach greater than about
95%.
[0101] In some aspects, one or more reactive single screw extruders
444 may be used to form the membrane 10, including a membrane
configured for a roofing membrane, that has one or more types of
silane-crosslinked polyolefin elastomers. For example, in some
aspects, one reactive single screw extruder 444 may be used to
produce and extrude a first silane-crosslinked polyolefin elastomer
associated with the top layer 14 of the membrane 10 (see FIG. 1),
while a second reactive single screw extruder 444 may be used to
produce and extrude a second silane-crosslinked polyolefin
elastomer associated with the bottom layer 38 of the membrane 10.
The complexity, architecture and required properties of the final
membrane 10 will determine the number and types of reactive single
screw extruders 444 employed according to the method 400 depicted
in FIG. 5.
[0102] It is understood that the prior description outlining and
teaching of the various membranes 10, and their respective
components and compositions, can be used in any combination, and
applies equally well to the method 400 for making the membrane 10
using the one-step Monosil process as shown in FIGS. 5 and 6.
Silane-Crosslinked Polyolefin Elastomer Physical Properties
[0103] A "thermoplastic", as used herein, is defined to mean a
polymer that softens when exposed to heat and returns to its
original condition when cooled to room temperature. A "thermoset",
as used herein, is defined to mean a polymer that solidifies and
irreversibly "sets" or "crosslinks" when cured. In either of the
Monosil or Sioplas processes described above, it is important to
understand the careful balance of thermoplastic and thermoset
properties of the various different materials used to produce the
final thermoset silane-crosslinked polyolefin elastomer or membrane
10, inclusive of membranes configured for roofing membrane
applications. Each of the intermediate polymer materials mixed and
reacted using a reactive twin screw extruder, and/or a reactive
single screw extruder are thermosets. Accordingly, the
silane-grafted polyolefin blend 276 and the silane-crosslinkable
polyolefin blend 298 are thermoplastics and can be softened by
heating so the respective materials can flow. Once the
silane-crosslinkable polyolefin blend 298 is extruded, molded,
pressed, and/or shaped into the uncured roofing membrane element or
other respective article, the silane-crosslinkable polyolefin blend
298 can begin to crosslink or cure at an ambient temperature and an
ambient humidity to form the membrane 10 (or other end product
form), as comprising one or more silane-crosslinked polyolefin
blends.
[0104] The thermoplastic/thermoset behavior of the
silane-crosslinkable polyolefin blend 298 and corresponding
silane-crosslinked polyolefin blend are important for the various
compositions and articles disclosed herein (e.g., membrane 10 shown
in FIG. 1, and membranes, layers and laminates for roofing membrane
and non-roofing applications) because of the potential energy
savings provided using these materials. For example, a manufacturer
can save considerable amounts of energy by being able to cure the
silane-crosslinkable polyolefin blend 298 at an ambient temperature
and an ambient humidity (e.g., as compared to a conventional EPDM
materials and processes for making the same). This curing process
is typically performed in the industry by applying significant
amounts of energy to heat or steam treat crosslinkable polyolefins
298. The ability to cure the inventive silane-crosslinkable
polyolefin blend 298 with ambient temperature and/or ambient
humidity is not a capability necessarily intrinsic to crosslinkable
polyolefins. Rather, this capability or property is dependent on
the relatively low density of the silane-crosslinkable polyolefin
blend 298. In some aspects, no additional curing overs, heating
ovens, steam ovens, or other forms of heat producing machinery
other than what was provided in the extruders are used to form the
silane-crosslinked polyolefin elastomers.
[0105] The specific gravity (or density) of the silane-crosslinked
polyolefin elastomer of the present disclosure may be lower than
the specific gravities of existing TPV and EPDM formulations used
in the art. The reduced specific gravity of these materials can
lead to lower weight parts, thereby facilitating additional
ease-of-assembly for roofers and other individuals charged with
installing the membranes 10 of the disclosure when employing as
roofing membranes. For example, the specific gravity of the
silane-crosslinked polyolefin elastomer of the present disclosure
may be from about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3, from
about 0.80 g/cm.sup.3to about 1.50 g/cm.sup.3, from about 1.25
g/cm.sup.3to about 1.45 g/cm.sup.3, from about 1.30 g/cm.sup.3 to
about 1.40 g/cm.sup.3, about 1.25 g/cm.sup.3, about 1.30
g/cm.sup.3, about 1.35 g/cm.sup.3, about 1.40 g/cm.sup.3, about
1.45 g/cm.sup.3, about 1.50 g/cm.sup.3, less than 1.75 g/cm.sup.3,
less than 1.60 g/cm.sup.3, less than 1.50 g/cm.sup.3, or less than
1.45 g/cm.sup.3, as compared to conventional TPV materials which
may have a specific gravity greater than 2.00 g/cm.sup.3and
conventional EPDM materials which may have a specific gravity of
from 2.0 g/cm.sup.3 to 3.0 g/cm.sup.3.
[0106] The stress/strain behavior of an exemplary
silane-crosslinked polyolefin elastomer of the present disclosure
(i.e., "silane-crosslinked polyolefin elastomer") relative to two
existing EPDM materials is provided. In particular, FIG. 7 displays
a smaller area between the stress/strain curves for the
silane-crosslinked polyolefin of the disclosure (labeled as "Silane
Cross-linked Polyolefin Elastomer" in FIG. 7), as compared to the
areas between the stress/strain curves of EPDM compound A and EPDM
compound B. This smaller area between the stress/strain curves for
the silane-crosslinked polyolefin elastomer can be desirable for
membranes 10, particularly as configured in a roofing membrane
form. Elastomeric materials typically have non-linear stress/strain
curves with a significant loss of energy when repeatedly stressed.
The silane-crosslinked polyolefin elastomers of the present
disclosure may exhibit greater elasticity and less viscoelasticity
(e.g., have linear curves and exhibit very low energy loss).
Embodiments of the silane-crosslinked polyolefin elastomers
described herein do not have any filler or plasticizer incorporated
into these materials so their corresponding stress/strain curves do
not have or display any Mullins effect and/or Payne effect. The
lack of Mullins effect for these silane-crosslinked polyolefin
elastomers is due to the lack of any filler or plasticizer added to
the silane-crosslinked polyolefin blend so the stress/strain curve
does not depend on the maximum loading previously encountered where
there is no instantaneous and irreversible softening. The lack of
Payne effect for these silane-crosslinked polyolefin elastomers is
due to the lack of any filler or plasticizer added to the
silane-crosslinked polyolefin blend so the stress/strain curve does
not depend on the small strain amplitudes previously encountered
where there is no change in the viscoelastic storage modulus based
on the amplitude of the strain.
[0107] The silane-crosslinked polyolefin elastomer or membrane 10
can exhibit a compression set of from about 5.0% to about 30.0%,
from about 5.0% to about 25.0%, from about 5.0% to about 20.0%,
from about 5.0% to about 15.0%, from about 5.0% to about 10.0%,
from about 10.0% to about 25.0%, from about 10.0% to about 20.0%,
from about 10.0% to about 15.0%, from about 15.0% to about 30.0%,
from about 15.0% to about 25.0%, from about 15.0% to about 20.0%,
from about 20.0% to about 30.0%, or from about 20.0% to about
25.0%, as measured according to ASTM D 395 (22 hrs @ 23.degree. C.,
70.degree. C., 80.degree. C., 90.degree. C., 125.degree. C., and/or
175.degree. C.). In other implementations, the silane-crosslinked
polyolefin elastomer or membrane 10 can exhibit a compression set
of from about 5.0% to about 20.0%, from about 5.0% to about 15.0%,
from about 5.0% to about 10.0%, from about 7.0% to about 20.0%,
from about 7.0% to about 15.0%, from about 7.0% to about 10.0%,
from about 9.0% to about 20.0%, from about 9.0% to about 15.0%,
from about 9.0% to about 10.0%, from about 10.0% to about 20.0%,
from about 10.0% to about 15.0%, from about 12.0% to about 20.0%,
or from about 12.0% to about 15.0%, as measured according to ASTM D
395 (22 hrs @ 23.degree. C., 70.degree. C., 80.degree. C.,
90.degree. C., 125.degree. C., and/or 175.degree. C.).
[0108] The silane-crosslinked polyolefin elastomer or membrane 10
may exhibit a crystallinity of from about 5% to about 40%, from
about 5% to about 25%, from about 5% to about 15%, from about 10%
to about 20%, from about 10% to about 15%, or from about 11% to
about 14% as determined using density measurements, differential
scanning calorimetry (DSC), X-Ray Diffraction, infrared
spectroscopy, and/or solid state nuclear magnetic spectroscopy. As
disclosed herein, DSC was used to measure the enthalpy of melting
in order to calculate the crystallinity of the respective
samples.
[0109] The silane-crosslinked polyolefin elastomer or membrane 10
may exhibit a glass transition temperature of from about
-75.degree. C. to about -25.degree. C., from about -65.degree. C.
to about -40.degree. C., from about -60.degree. C. to about
-50.degree. C., from about -50.degree. C. to about -25.degree. C.,
from about -50.degree. C. to about -30.degree. C., or from about
-45.degree. C. to about -25.degree. C. as measured according to
differential scanning calorimetry (DSC) using a second heating run
at a rate of 5.degree. C./min or 10.degree. C./min.
[0110] The silane-crosslinked polyolefin elastomer, membrane 10
(e.g., as including top and bottom layers 14, 38), a membrane 10
configured as a roofing membrane, and any membrane or comparable
structure may exhibit a weathering color difference of from about
0.25 .DELTA.E to about 2 .DELTA.E, from about 0.25 .DELTA.E to
about 1.5 .DELTA.E, from about 0.25 .DELTA.E to about 1.0 .DELTA.E,
or from about 0.25 .DELTA.E to about 0.5 .DELTA.E, as measured
according to ASTM D2244. In some implementations, the
silane-crosslinked polyolefin elastomer, membrane 10 (e.g., as
including top and bottom layers 14, 38), membrane 10 configured as
a roofing membrane, and any membrane or comparable structure may
exhibit a weathering color difference of about 0.20 .DELTA.E, 0.30
.DELTA.E, 0.40 .DELTA.E, 0.5 .DELTA.E, 0.6 .DELTA.E, 0.7 .DELTA.E,
0.8 .DELTA.E, 0.9 .DELTA.E, 1.0 .DELTA.E, 1.1 .DELTA.E, 1.2
.DELTA.E, 1.3 .DELTA.E, 1.4 .DELTA.E, 1.5 .DELTA.E, 1.6 .DELTA.E,
1.7 .DELTA.E, 1.8 .DELTA.E, 1.9 .DELTA.E, 2.0 .DELTA.E, and all
weathering color difference values between these amounts, as
measured according to ASTM D2244. In some embodiments, the membrane
10 may be a high-load flame retardant thermoplastic polyolefin
(TPO) having the above weathering properties.
[0111] The silane-crosslinked polyolefin elastomer, membrane 10
(e.g., as including top and bottom layers 14, 38), membrane 10
configured as a roofing membrane, and any membrane or comparable
structure may exhibit a weathering color difference from about 0.4
.DELTA.E to about 0.8 .DELTA.E, or about 0.5 .DELTA.E to about 0.7
.DELTA.E, after 1000 cycles of testing ("1000 k") according to the
ASTM G155. These structures also may exhibit a weathering color
difference from about 0.4 .DELTA.E to about 3 .DELTA.E, from about
0.4 .DELTA.E to about 2 .DELTA.E, from about 1 .DELTA.E to about
1.5 .DELTA.E, or from about 1.1 .DELTA.E to about 1.3 .DELTA.E,
after 2000 cycles of testing ("2000 k") according to ASTM G155.
Accordingly, in some implementations, these structures may exhibit
a weathering color difference of 0.40 .DELTA.E, 0.5 .DELTA.E, 0.6
.DELTA.E, 0.7 .DELTA.E, 0.8 .DELTA.E, 0.9 .DELTA.E, 1.0 .DELTA.E,
1.1 .DELTA.E, 1.2 .DELTA.E, 1.3 .DELTA.E, 1.4 .DELTA.E, 1.5
.DELTA.E, 1.6 .DELTA.E, 1.7 .DELTA.E, 1.8 .DELTA.E, 1.9 .DELTA.E,
2.0 .DELTA.E, 2.1 .DELTA.E, 2.2 .DELTA.E, 2.3 .DELTA.E, 2.4
.DELTA.E, 2.5 .DELTA.E, 2.6 .DELTA.E, 2.7 .DELTA.E, 2.8 .DELTA.E,
2.9 .DELTA.E, 3.0 .DELTA.E, and all weathering color difference
values between these amounts, as measured according to ASTM G155 at
1000 cycles or 2000 cycles of testing.
[0112] The silane-crosslinked polyolefin elastomer, membrane 10
(e.g., as including top and bottom layers 14, 38), membrane 10
configured as a roofing membrane, and any membrane or comparable
structure may exhibit heat aging resistance with regard to retained
tensile strength, elongation and modulus properties after exposure
to 115.degree. C. for 168 hours. More particularly, these
structures can exhibit a tensile strength from about 5 MPa to about
15 MPa, from about 9 MPa to about 15 MPa, or from about 9.5 MPa to
about 11.5 MPa, after exposure to 115.degree. C. for 168 hours.
These structures can also exhibit an elongation from about 100% to
about 1000%, from about 100% to about 750%, from about 100% to
about 500%, from about 100% to about 300%, from about 150% to about
300%, or from about 160% to about 270%, after exposure to
115.degree. C. for 168 hours. Further, these structures can exhibit
an elastic modulus at 100% elongation (i.e., a 100% elastic
modulus) from about 3 MPa to about 12 MPa, from about 6 MPa to
about 10 MPa, or from about 6.6 MPa to about 9.0 MPa, after
exposure to 115.degree. C. for 168 hours.
EXAMPLES
[0113] The following non-limiting examples are provided as
exemplary embodiments to further outline aspects of the
disclosure.
Materials
[0114] All chemicals, constituents and precursors were obtained
from commercial suppliers and used as provided without further
purification.
Example 1--Preparation of a Silane-Grafted Polyolefin Elastomer
[0115] Example 1 (Ex. 1) was produced by extruding 82.55 wt. %
ethylene/.alpha.-olefin copolymer and 14.45 wt. % propylene
homopolymer together with 3.0 wt. % silane crosslinking agent to
form a silane-grafted polyolefin elastomer, according to one of the
foregoing methods outlined in the disclosure. The Example 1
silane-grafted polyolefin elastomer was then extruded using various
condensation catalysts and fillers to form a silane-crosslinkable
polyolefin elastomer, as suitable for top and bottom layers 14, 38
of a roofing membrane (as described below in Example 2), a membrane
for any other use, or a comparable structure. The composition of
the Example 1 silane-grafted polyolefin elastomer is provided in
Table 1 below.
TABLE-US-00001 TABLE 1 Silane-grafted polyolefin elastomer Ex. 1
Ingredients (wt. %) ethylene/.alpha.-olefin copolymers 82.55
polypropylene homopolymer 14.45 silane crosslinker 3.00 TOTAL
100
Example 2--Preparation of a Roofing Membrane
[0116] In this example, identical top and bottom layers 14, 38 were
used to produce an embodiment of a single ply membrane 10
configured as a roofing membrane. In particular, the top and bottom
layers 14 38 were produced by extruding 29.0 wt. % silane-grafted
polyolefin elastomer (from Example 1) and 70.0 wt. % vinyl silane
coated magnesium di hydroxide, Mg(OH).sub.2 (MDH), together with
1.0 wt. % dioctyltin dilaurate (DOTL) condensation catalyst to form
a silane-crosslinkable polyolefin elastomer blend. The blend was
then extruded and calendared to provide the respective top and
bottom layers 14, 38 of an uncured membrane element. The
silane-crosslinkable polyolefin elastomer of the layers 14, 38 of
the uncured membrane element was then cured at ambient temperature
and humidity to form the membrane 10. The composition of the
membrane 10 formed in this example is provided in Table 2 below
(labeled as "Ex. 2").
Example 3--Preparation of a Roofing Membrane
[0117] In this example, identical top and bottom layers 14, 38 were
used to produce another embodiment of a single ply membrane 10
configured as a roofing membrane. In particular, the top and bottom
layers 14, 38 were produced by extruding 29.0 wt. % silane-grafted
polyolefin elastomer (from Example 1) and 70.0 wt. % stearic
acid-coated magnesium di hydroxide, Mg(OH).sub.2 (MDH), together
with 1.0 wt. % dioctyltin dilaurate (DOTL) condensation catalyst to
form a silane-crosslinkable polyolefin elastomer blend. The blend
was then extruded and calendared to provide the respective top and
bottom layers 14, 38 of an uncured membrane element. The
silane-crosslinkable polyolefin elastomer of the layers 14, 38 of
the uncured membrane element was then cured at ambient temperature
and humidity to form the membrane 10. The composition of the
membrane 10 formed in this example is also provided in Table 2
below (labeled as "Ex. 3").
TABLE-US-00002 TABLE 2 Comparison of Roofing Membranes elastomer
vinyl silane- stearic acid- DOTL from Ex. 1 coated MDH coated MDH
Catalyst Example Sample (wt. %) (wt. %) (wt. %) (wt. %) Ex. 2 Top
Layer 29 70 -- 1 Ex. 2 Bottom 29 70 -- 1 Layer Ex. 3 Top Layer 29
-- 70 1 Ex. 3 Bottom 29 -- 70 1 Layer
Example 4--Preparation of a Roofing Membrane
[0118] In this example, identical top and bottom layers 14, 38 were
used to produce another embodiment of a single ply membrane 10
configured as a roofing membrane. In particular, the top and bottom
layers 14, 38 were produced by extruding silane-grafted polyolefin
elastomer, a flame retardant (magnesium di hydroxide), together
with a condensation catalyst to form a silane-crosslinkable
polyolefin elastomer blend, according to one of the foregoing
methods of the disclosure. As shown below in Table 3, these
constituents were blended at different amounts to form the
silane-crosslinkable polyolefin elastomers of this example, denoted
Ex. 4-1, Ex. 4-2 and Ex. 4-3.
TABLE-US-00003 TABLE 3 Comparison of silane-grafted polyolefin
elastomers Thermoplastic portion Grafted portion fire retardant
acrylic ethylene/.alpha.- ethylene propylene silane
(MgOH.sub.2)/anti-oxidant/ polymer olefin monomer & acrylic
crosslinking UV protectant carrier copolymer polymer carrier agent
(wt. %) (wt. %) (wt. %) (wt. %) (wt. %) Ex. 4-1 50.54 19.46 20.46
9.00 0.54 Ex. 4-2 57.76 22.24 13.64 6.00 0.36 Ex. 4-3 57.76 22.24
13.64 6.0 0.36
[0119] The blend was then extruded and calendared to provide the
respective top and bottom layers 14, 38 of an uncured membrane
element. The extrusion was conducted on a single-screw extruder
with nine (9) zones set the following temperatures: 100.degree. C.
(Z1), 140.degree. C. (Z2), 155.degree. C. (Z3), 140.degree. C.
(Z4), 140.degree. C. (Z5), and 130.degree. C. (Z6-Z9). The extruder
was set to extrude at a screw rotational rate of 145 rpm, a load of
55% and a throughput of 150 kg/hr. The average temperature of the
extrudate melt was measured to be 131.degree. C. with a pressure of
about 55 bars. Further, the die of the extruder employed in this
example is 1016 mm.times.2.3 mm and the extrudate sheet was
measured at about 880 mm.times.1.5 mm. As the extrudate sheet was
directed out of the extruder at a line speed of about 3 m/min, the
sheet was calendared by a 3-roll calendaring apparatus with each
roll set at a temperature of about 21.degree. C. (ambient).
[0120] The silane-crosslinkable polyolefin elastomer of the layers
14, 38 of the uncured membrane element was then cured at ambient
temperature and humidity to form the membrane 10, as suitable for a
roofing membrane. Heat aging and weathering resistance is provided
in Table 4 for the three roofing membrane samples prepared in this
example (i.e., Ex. 4-1 through 4-3). In each of the cells in Table
4, the top values correspond with measurements with the grain and
the bottom values correspond with measurements against the
grain.
TABLE-US-00004 TABLE 4 Heat aging and weathering resistance data
for roofing membranes Ex. 4-1 Ex. 4-2 Ex. 4-3 Heat aging data
Tensile Strength (MPa) 9.76 10.09 10.02 10.48 11.12 10.75
Elongation (%) 247.92 182.2 161.7 257.38 190.24 179.79 100% Modulus
(MPa) 6.92 8.35 8.81 7.22 8.9 9.04 Weathering data .DELTA.E (1000k)
0.65 0.59 0.49 .DELTA.E (2000k) 1.20 1.11 1.33
Example 5
[0121] In this example, identical top and bottom layers 14, 38 were
used to produce another embodiment of a single ply membrane 10
configured as a roofing membrane. In particular, the top and bottom
layers 14, 38 were produced by extruding silane-grafted polyolefin
elastomer, a flame retardant (magnesium di hydroxide), together
with a condensation catalyst to form a silane-crosslinkable
polyolefin elastomer blend, according to one of the foregoing
methods of the disclosure. In particular, the elastomer blend of
this example was formed by blending and extruding 34 wt. %
ethylene/.alpha.-olefin copolymer, 7.5 wt. % olefin block
copolymer, 7.5 wt. % propylene/.alpha.-olefin copolymer and 1%
silane crosslinking agent with 4.1 wt. % acrylic polymer carrier
and 45.9 wt. % fire retardant (MgOH.sub.2), anti-oxidant and
UV-protectant mixture. Further, the blend was extruded and
calendared according to the same parameters and conditions as
employed in Example 4 to provide the respective top and bottom
layers 14, 38 of an uncured membrane element.
[0122] The silane-crosslinkable polyolefin elastomer of the layers
14, 38 of the resulting uncured membrane element was then cured at
ambient temperature and humidity to form the membrane 10, as
suitable for a roofing membrane. Material properties for samples
from this example (N=3) are provided below in Table 5 (i.e., Ex.
5-1). In each of the cells in Table 5, the top values correspond
with measurements with the grain and the bottom values correspond
with measurements against the grain.
TABLE-US-00005 TABLE 5 Material properties for roofing membrane
Elon- 100% 300% Tear Durometer Tensile gation Modulus Modulus Die C
Sample (ShA) (MPa) (%) (MPa) (MPa) (N/mm) Ex. 5-1 80 11.01 758.17
3.82 5.64 41.44 (with grain) Ex. 5-1 78 9.87 658.33 4.13 5.98 41.44
(against grain)
[0123] Referring now to FIGS. 8A and 8B, stress vs. elongation
plots are provided of the Ex. 5-1 membranes, with and against the
grain. These membranes comprise a silane-crosslinked polyolefin
elastomer suitable for roofing membranes. As is evident from these
figures and Table 5 above, the tensile strength of these membranes
approach and exceed 10 MPa (i.e., 11.01 MPa and 9.87 MPa for
samples with and against the grain, respectively) with an
elongation in excess of 600% (i.e., 658% and 758% for samples with
and against the grain, respectively).
[0124] Referring now to FIG. 9, the thermal stability of Ex. 1
prepared in Example 1 (labeled in FIG. 9 as "Ex. 1") is provided
with respect to a comparative EPDM peroxide crosslinked resin and a
comparative EPDM sulfur crosslinked resin (labeled in FIG. 9 as
"EPDM Peroxide" and "EPDM Sulfur", respectively). As shown, Ex. 1
can retain nearly 90% of its elastic properties at 150.degree. C.
for greater than 500 hrs. The retention of elastic properties as
provided in Example 1 is representative of each of the inventive
silane-crosslinked polyolefin elastomers disclosed herein. The
roofing member made from these silane-crosslinked polyolefin
elastomers may retain up to 60%, 70%, 80%, or 90% of its elastic
properties as determined by using Stress Relaxation measurements at
150.degree. C. for greater than 100 hrs, greater than 200 hrs,
greater than 300 hrs, greater than 400 hrs, and greater than 500
hrs.
[0125] Referring now to FIG. 10, compression set values are
provided across a time period of 4,000 hrs for the Ex. 1
silane-grafted polyolefin elastomer and a comparative EPDM sample.
More particularly, FIG. 10 demonstrates the superior long term
retention of elastic properties of the silane-crosslinked
polyolefin elastomer material, Ex. 1, which is representative of
the silane-grafted polyolefin elastomers in this disclosure than
can be used to make the membrane 10. As provided, the Ex. 1
silane-crosslinked polyolefin elastomer material maintains a
compression set of 35% or lower as measured according to ASTM D 395
(30% @ 110.degree. C.). In contrast, the comparative EPDM sample
exhibits a significant drop in its compression set levels after 750
hours of exposure to 110.degree. C. As such, FIG. 10 provides
evidence that the silane-crosslinked polyolefin elastomer materials
used in the membranes 10 of the disclosure, e.g., as configured in
a roofing membrane, retain their elasticity (compression set %)
over a long period of time upon exposure to heat, which simulates
exterior weathering or aging of roofing materials.
[0126] It is also important to note that the construction and
arrangement of the elements of the device as shown in the exemplary
embodiments is illustrative only. Further, it will be understood
that any described processes or steps within described processes
may be combined with other disclosed processes or steps to form
structures within the scope of the present device. Although only a
few embodiments of the present innovations have been described in
detail in this disclosure, those skilled in the art who review this
disclosure will readily appreciate that many modifications are
possible (e.g., variations in sizes, dimensions, structures, shapes
and proportions of the various elements, values of parameters,
mounting arrangements, use of materials, colors, orientations,
etc.) without materially departing from the novel teachings and
advantages of the subject matter recited. For example, elements
shown as integrally formed may be constructed of multiple parts or
elements shown as multiple parts may be integrally formed, the
operation of the interfaces may be reversed or otherwise varied,
the length or width of the structures and/or members or connector
or other elements of the system may be varied, the nature or number
of adjustment positions provided between the elements may be
varied. It should be noted that the elements and/or assemblies of
the system may be constructed from any of a wide variety of
materials that provide sufficient strength or durability, in any of
a wide variety of colors, textures, and combinations. Accordingly,
all such modifications are intended to be included within the scope
of the present innovations. Other substitutions, modifications,
changes, and omissions may be made in the design, operating
conditions, and arrangement of the desired and other exemplary
embodiments without departing from the spirit of the present
innovations.
LISTING OF NON-LIMITING EMBODIMENTS
[0127] Embodiment A is a roofing membrane comprising: a top layer
comprising a flame retardant and a first silane-crosslinked
polyolefin elastomer having a density less than 0.90 g/cm.sup.3; a
scrim layer; and a bottom layer comprising a flame retardant and a
second silane-crosslinked polyolefin elastomer having a density
less than 0.90 g/cm.sup.3, wherein the top and bottom layers of the
single ply roofing membrane both exhibit a compression set of from
about 5.0% to about 35.0%, as measured according to ASTM D 395 (22
hrs @ 70.degree. C.).
[0128] The roofing membrane of Embodiment A wherein the compression
set is from about 10% to about 30%.
[0129] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first and second
silane-crosslinked polyolefin elastomers both exhibit a
crystallinity of from about 5% to about 25%.
[0130] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first and second
silane-crosslinked polyolefin elastomers have a glass transition
temperature of from about -75.degree. C. to about -25.degree.
C.
[0131] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first and second
silane-crosslinked polyolefin elastomers each comprise a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
[0132] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the density is from about
0.85 g/cm.sup.3 to about 0.89 g/cm.sup.3.
[0133] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the single ply roofing
membrane exhibits a weathering color difference of from about 0.25
.DELTA.E to about 2.0 .DELTA.E, as measured according to ASTM
D2244.
[0134] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first
silane-crosslinked polyolefin elastomer and the second
silane-crosslinked polyolefin elastomer are chemically distinct
from each other.
[0135] Embodiment B is a method of making a roofing membrane, the
method comprising: extruding a first silane-crosslinkable
polyolefin elastomer to form a top layer; extruding a second
silane-crosslinkable polyolefin elastomer to form a bottom layer;
calendaring a scrim layer between the top and the bottom layers to
form an uncured roofing membrane element; and crosslinking the
silane-crosslinkable polyolefin elastomers of the top and the
bottom layers in the uncured roofing membrane element at a curing
temperature and a curing humidity to form the single ply roofing
membrane, wherein the top and bottom layers of the single ply
roofing membrane both exhibit a compression set of from about 5.0%
to about 35.0%, as measured according to ASTM D 395 (22 hrs @
70.degree. C.).
[0136] The method of Embodiment B wherein the first
silane-crosslinkable polyolefin elastomer and the second
silane-crosslinkable polyolefin elastomer are chemically distinct
from each other.
[0137] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the curing temperature is an ambient
temperature.
[0138] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the curing humidity is an ambient
humidity.
[0139] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the first and second
silane-crosslinkable polyolefin elastomers each comprise a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
[0140] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the single ply roofing membrane
exhibits a weathering color difference of from about 0.25 .DELTA.E
to about 2.0 .DELTA.E, as measured according to ASTM D2244.
[0141] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the single ply roofing membrane
exhibits a flame retardance rating of classification D as measured
in accordance with the EN ISO 11925-2 surface exposure test.
[0142] Embodiment C is a method of making a high-load flame
retardant thermoplastic polyolefin (TPO) roofing membrane, the
method comprising: adding a silane-grafted polyolefin elastomer, a
flame retardant, and a condensation catalyst to a reactive single
screw extruder to produce a silane-crosslinkable polyolefin
elastomer; calendaring the silane-crosslinkable polyolefin
elastomer to form a top layer and a bottom layer; calendaring a
scrim layer between the top and the bottom layers to form an
uncured roofing membrane element; and crosslinking the
silane-crosslinkable polyolefin elastomers of the top and the
bottom layers in the uncured roofing membrane element at an ambient
temperature and an ambient humidity to form the thermoplastic
polyolefin (TPO) roofing membrane, wherein the top and bottom
layers of the thermoplastic polyolefin (TPO) roofing membrane both
exhibit a compression set of from about 5.0% to about 35.0%, as
measured according to ASTM D 395 (22 hrs @ 70.degree. C.).
[0143] The method of Embodiment C wherein the top and bottom layers
are chemically equivalent to each other.
[0144] The method of Embodiment C or Embodiment C with any of the
intervening features wherein the single ply roofing membrane
exhibits a flame retardance rating of classification D as measured
in accordance with the EN ISO 11925-2 surface exposure test.
[0145] The method of Embodiment C or Embodiment C with any of the
intervening features wherein the silane-grafted polyolefin
elastomer comprises a first polyolefin having a density less than
0.86 g/cm.sup.3, a second polyolefin, a silane crosslinker, a
grafting initiator.
[0146] The method of Embodiment C or Embodiment C with any of the
intervening features wherein the high-load flame retardant
thermoplastic polyolefin (TPO) roofing membrane exhibits a
weathering color difference of from about 0.25 .DELTA.E to about
2.0 .DELTA.E, as measured according to ASTM D2244.
[0147] Embodiment D is a membrane, comprising: at least one layer
comprising a first silane-crosslinked polyolefin elastomer having a
density from about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3.
[0148] The membrane of Embodiment D wherein the first
silane-crosslinked polyolefin elastomer exhibits a crystallinity of
from about 5% to about 25% and a glass transition temperature of
from about -75.degree. C. to about -25.degree. C.
[0149] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the first silane-crosslinked
polyolefin elastomer comprises a first polyolefin having a density
less than 0.90 g/cm.sup.3, a second polyolefin, a silane
crosslinker, a grafting initiator, and a condensation catalyst.
[0150] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the first silane-crosslinked
polyolefin elastomer is selected from the group consisting of a
propylene/.alpha.-olefin copolymer and a blend of
propylene/.alpha.-olefin copolymer with an ethylene/.alpha.-olefin
copolymer.
[0151] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the at least one layer comprises a
thickness from about 0.2 mm to about 3 mm.
[0152] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the at least one layer comprises a
first silane-crosslinked polyolefin elastomer having a density from
about 0.80 g/cm.sup.3 to about 1.45 g/cm.sup.3, and further wherein
the first silane-crosslinked polyolefin elastomer comprises a first
polyolefin having a density less than 0.90 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
[0153] The membrane of Embodiment D or Embodiment D with any
intervening features further comprising: a scrim layer that is
contiguous with the at least one layer.
[0154] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the membrane is configured as a
roofing membrane.
[0155] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the at least one layer is
characterized by a weathering color difference from about 0.4
.DELTA.E to about 3 .DELTA.E after 2000 cycles of testing, as
measured according to ASTM G155, and further wherein the at least
one layer is characterized by a heat aging resistance after
exposure to 115.degree. C. for 168 hours given by a tensile
strength from about 5 MPa to about 15 MPa, an elongation from about
100% to about 300%, and a 100% elastic modulus from about 3 MPa to
about 12 MPa.
[0156] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the at least one layer is further
characterized by a heat aging resistance after exposure to
115.degree. C. for 168 hours given by a tensile strength from about
9.5 MPa to about 11.5 MPa, an elongation from about 100% to about
1000%, and a 100% elastic modulus from about 6.6 MPa to about 9.0
MPa.
[0157] The membrane of Embodiment D or Embodiment D with any
intervening features wherein the at least one layer further
comprises a flame retardant, the flame retardant comprising
magnesium di hydroxide or aluminum tri hydroxide from about 20 wt.
% to about 70 wt. %.
[0158] Embodiment E is a membrane, comprising: a first layer
comprising a first silane-crosslinked polyolefin elastomer having a
density from about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3; and a
second layer comprising a second silane-crosslinked polyolefin
elastomer having a density from about 0.80 g/cm.sup.3to about 1.75
g/cm.sup.3.
[0159] The membrane of Embodiment E wherein one or both of the
first and second silane-crosslinked polyolefin elastomers exhibits
a crystallinity of from about 5% to about 25% and a glass
transition temperature of from about -75.degree. C. to about
-25.degree. C.
[0160] The membrane of Embodiment E or Embodiment E with any
intervening features wherein one or both of the first and second
silane-crosslinked polyolefin elastomers comprises a first
polyolefin having a density less than 0.90 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
[0161] The membrane of Embodiment E or Embodiment E with any
intervening features wherein one or both of the first and second
silane-crosslinked polyolefin elastomers is selected from the group
consisting of a propylene/.alpha.-olefin copolymer and a blend of
propylene/.alpha.-olefin copolymer with an ethylene/.alpha.-olefin
copolymer.
[0162] Embodiment F is a method of making a membrane, comprising:
processing a composition comprising a first polyolefin having a
density less than 0.90 g/cm.sup.3, a second polyolefin, a silane
crosslinker, a grafting initiator, and a condensation catalyst to
form at least one layer; and crosslinking the at least one layer at
a curing temperature and a curing humidity, wherein the
crosslinking is conducted until the at least one layer comprises a
density from about 0.80 g/cm.sup.3to about 1.75 g/cm.sup.3.
[0163] The method of Embodiment F wherein the curing temperature is
an ambient temperature.
[0164] The method of Embodiment F or Embodiment F with any
intervening features wherein the curing humidity is an ambient
humidity.
[0165] The method of Embodiment F or Embodiment F with any
intervening features wherein the processing comprises one or more
process steps selected from the group consisting of extruding, blow
molding, casting and calendaring.
[0166] The method of Embodiment F or Embodiment F with any
intervening features further comprising: processing a scrim layer
with the at least one layer such that the scrim layer is contiguous
to the at least one layer.
* * * * *